diff --git a/ebos/eclbasevanguard.hh b/ebos/eclbasevanguard.hh
index a2f97f8ca..ab62b5222 100644
--- a/ebos/eclbasevanguard.hh
+++ b/ebos/eclbasevanguard.hh
@@ -65,7 +65,7 @@ struct EnableOpmRstFile {
     using type = UndefinedProperty;
 };
 template<class TypeTag, class MyTypeTag>
-struct EclStrictParsing {
+struct ParsingStrictness {
     using type = UndefinedProperty;
 };
 template<class TypeTag, class MyTypeTag>
@@ -134,8 +134,8 @@ struct EnableOpmRstFile<TypeTag, TTag::EclBaseVanguard> {
     static constexpr bool value = false;
 };
 template<class TypeTag>
-struct EclStrictParsing<TypeTag, TTag::EclBaseVanguard> {
-    static constexpr bool value = false;
+struct ParsingStrictness<TypeTag, TTag::EclBaseVanguard> {
+    static constexpr auto value = "normal";
 };
 template<class TypeTag>
 struct SchedRestart<TypeTag, TTag::EclBaseVanguard> {
@@ -231,8 +231,11 @@ public:
                              "Include OPM-specific keywords in the ECL restart file to enable restart of OPM simulators from these files");
         EWOMS_REGISTER_PARAM(TypeTag, std::string, IgnoreKeywords,
                              "List of Eclipse keywords which should be ignored. As a ':' separated string.");
-        EWOMS_REGISTER_PARAM(TypeTag, bool, EclStrictParsing,
-                             "Use strict mode for parsing - all errors are collected before the applicaton exists.");
+        EWOMS_REGISTER_PARAM(TypeTag, std::string, ParsingStrictness,
+                             "Set strictness of parsing process. Available options are "
+                             "normal (stop for critical errors), "
+                             "high (stop for all errors) and "
+                             "low (as normal, except do not stop due to unsupported keywords even if marked critical");
         EWOMS_REGISTER_PARAM(TypeTag, bool, SchedRestart,
                              "When restarting: should we try to initialize wells and groups from historical SCHEDULE section.");
         EWOMS_REGISTER_PARAM(TypeTag, int, EdgeWeightsMethod,
@@ -290,7 +293,6 @@ public:
 #endif
         enableDistributedWells_ = EWOMS_GET_PARAM(TypeTag, bool, AllowDistributedWells);
         ignoredKeywords_ = EWOMS_GET_PARAM(TypeTag, std::string, IgnoreKeywords);
-        eclStrictParsing_ = EWOMS_GET_PARAM(TypeTag, bool, EclStrictParsing);
         int output_param = EWOMS_GET_PARAM(TypeTag, int, EclOutputInterval);
         if (output_param >= 0)
             outputInterval_ = output_param;
diff --git a/ebos/eclgenericvanguard.cc b/ebos/eclgenericvanguard.cc
index bb88829cd..d64b73e5d 100644
--- a/ebos/eclgenericvanguard.cc
+++ b/ebos/eclgenericvanguard.cc
@@ -133,7 +133,7 @@ void EclGenericVanguard::readDeck(const std::string& filename)
                   modelParams_.actionState_,
                   modelParams_.wtestState_,
                   modelParams_.eclSummaryConfig_,
-                  nullptr, false, false, false, {});
+                  nullptr, "normal", false, false, {});
     modelParams_.setupTime_ = setupTimer.stop();
 }
 
diff --git a/ebos/eclgenericvanguard.hh b/ebos/eclgenericvanguard.hh
index 3fdffd4ee..0f0edcb74 100644
--- a/ebos/eclgenericvanguard.hh
+++ b/ebos/eclgenericvanguard.hh
@@ -296,7 +296,6 @@ protected:
 #endif
     bool enableDistributedWells_;
     std::string ignoredKeywords_;
-    bool eclStrictParsing_;
     std::optional<int> outputInterval_;
     bool useMultisegmentWell_;
     bool enableExperiments_;
diff --git a/opm/simulators/flow/KeywordValidation.cpp b/opm/simulators/flow/KeywordValidation.cpp
index d4d09297d..4fa3df6a3 100644
--- a/opm/simulators/flow/KeywordValidation.cpp
+++ b/opm/simulators/flow/KeywordValidation.cpp
@@ -27,10 +27,12 @@
 
 #include <fmt/format.h>
 
+#include <opm/common/OpmLog/OpmLog.hpp>
 #include <opm/common/utility/OpmInputError.hpp>
 #include <opm/input/eclipse/Deck/Deck.hpp>
 #include <opm/input/eclipse/Deck/DeckKeyword.hpp>
 #include <opm/input/eclipse/Parser/ErrorGuard.hpp>
+#include <opm/input/eclipse/Parser/InputErrorAction.hpp>
 #include <opm/input/eclipse/Parser/ParseContext.hpp>
 #include <opm/simulators/flow/KeywordValidation.hpp>
 
@@ -43,7 +45,7 @@ namespace KeywordValidation
 {
 
 
-    std::string get_error_report(const std::vector<ValidationError>& errors, const bool critical)
+    std::string get_error_report(const std::vector<ValidationError>& errors, const bool include_noncritical, const bool include_critical)
     {
         const std::string keyword_format = "  {keyword}: keyword not supported\n";
         const std::string item_format1 = "  {{keyword}}: invalid value '{}' for item {}\n";
@@ -52,7 +54,7 @@ namespace KeywordValidation
 
         std::string report;
         for (const ValidationError& err : errors) {
-            if (err.critical == critical) {
+            if ((err.critical && include_critical) || (!err.critical && include_noncritical)) {
                 if (err.item_number && err.item_value) {
                     std::string message;
                     if (err.record_number == 0) {
@@ -84,6 +86,7 @@ namespace KeywordValidation
     void
     KeywordValidator::validateDeck(const Deck& deck,
                                    const ParseContext& parse_context,
+                                   const bool treat_critical_as_noncritical,
                                    ErrorGuard& error_guard) const
     {
         // Make a vector with all problems encountered in the deck.
@@ -98,18 +101,31 @@ namespace KeywordValidation
             }
         }
 
-        // First report non-critical problems as a warning.
-        auto warning_report = get_error_report(errors, false);
-        if (!warning_report.empty()) {
-            parse_context.handleError(
-                ParseContext::SIMULATOR_KEYWORD_NOT_SUPPORTED, warning_report, std::nullopt, error_guard);
-        }
+        if (treat_critical_as_noncritical) {
+            // Get both critical and noncritical errors.
+            auto warning_report = get_error_report(errors, true, true);
+            if (!warning_report.empty()) {
+                // Report all as warnings.
+                parse_context.handleError(ParseContext::SIMULATOR_KEYWORD_NOT_SUPPORTED, warning_report, std::nullopt, error_guard);
+            }
+        } else {
+            // First report non-critical problems as a warning.
+            auto warning_report = get_error_report(errors, true, false);
+            if (!warning_report.empty()) {
+                parse_context.handleError(
+                                          ParseContext::SIMULATOR_KEYWORD_NOT_SUPPORTED, warning_report, std::nullopt, error_guard);
+            }
 
-        // Then report critical problems as an error.
-        auto error_report = get_error_report(errors, true);
-        if (!error_report.empty()) {
-            parse_context.handleError(
-                ParseContext::SIMULATOR_KEYWORD_NOT_SUPPORTED_CRITICAL, error_report, std::nullopt, error_guard);
+            // Then report critical problems as an error.
+            auto error_report = get_error_report(errors, false, true);
+            if (!error_report.empty()) {
+                OpmLog::info("\nOPM Flow will terminate due to unsupported critical keywords.\n"
+                             "These are keywords that would change the simulator results if supported.\n"
+                             "If you need to override this behaviour, you can use the command line argument --parsing-strictness=low,\n"
+                             "this will reduce the severity of this to a warning instead of an error.");
+                parse_context.handleError(
+                                          ParseContext::SIMULATOR_KEYWORD_NOT_SUPPORTED_CRITICAL, error_report, std::nullopt, error_guard);
+            }
         }
     }
 
diff --git a/opm/simulators/flow/KeywordValidation.hpp b/opm/simulators/flow/KeywordValidation.hpp
index 98d765eb1..e78df09ed 100644
--- a/opm/simulators/flow/KeywordValidation.hpp
+++ b/opm/simulators/flow/KeywordValidation.hpp
@@ -78,11 +78,12 @@ namespace KeywordValidation
     };
 
     // Get a formatted error report from a vector of validation errors. Set
-    // critical to true if the report should contain only critical errors. If
-    // critical is false, only non-critical errors are reported. If not
-    // critical/non-critical errors are present, but the critical flag to reset
-    // them, the result will be an empty string.
-    std::string get_error_report(const std::vector<ValidationError>& errors, const bool critical);
+    // include_noncritical to true if the report should include noncritical errors, and
+    // include_critical to true if the report should include critical errors. These may
+    // be set independently. If no errors are included the result will be an empty string.
+    std::string get_error_report(const std::vector<ValidationError>& errors,
+                                 const bool include_noncritical,
+                                 const bool include_critical);
 
 
 
@@ -109,9 +110,12 @@ namespace KeywordValidation
 
         // Validate a deck, reporting warnings and errors. If there are only
         // warnings, these will be reported. If there are errors, these are
-        // reported, and execution of the program is halted.
+        // reported, and execution of the program is halted, unless the argument
+        // treat_critical_as_noncritical is true, then these also will only be
+        // reported and not cause termination.
         void validateDeck(const Deck& deck,
                           const ParseContext& parse_context,
+                          const bool treat_critical_as_noncritical,
                           ErrorGuard& error_guard) const;
 
         // Validate a single deck keyword. If a problem is encountered, add the
diff --git a/opm/simulators/flow/Main.cpp b/opm/simulators/flow/Main.cpp
index cf44e423d..347004851 100644
--- a/opm/simulators/flow/Main.cpp
+++ b/opm/simulators/flow/Main.cpp
@@ -171,7 +171,7 @@ void Main::readDeck(const std::string& deckFilename,
                     const std::string& outputMode,
                     const bool init_from_restart_file,
                     const bool allRanksDbgPrtLog,
-                    const bool strictParsing,
+                    const std::string& parsingStrictness,
                     const int mpiRank,
                     const int output_param,
                     const std::string& parameters,
@@ -202,7 +202,7 @@ void Main::readDeck(const std::string& deckFilename,
                   wtestState_,
                   summaryConfig_,
                   std::make_shared<Python>(),
-                  strictParsing,
+                  parsingStrictness,
                   init_from_restart_file,
                   outputCout_,
                   outputInterval);
diff --git a/opm/simulators/flow/Main.hpp b/opm/simulators/flow/Main.hpp
index 498f44d43..dd1283f01 100644
--- a/opm/simulators/flow/Main.hpp
+++ b/opm/simulators/flow/Main.hpp
@@ -374,7 +374,7 @@ private:
                            EWOMS_GET_PARAM(PreTypeTag, std::string, OutputMode),
                            !EWOMS_GET_PARAM(PreTypeTag, bool, SchedRestart),
                            EWOMS_GET_PARAM(PreTypeTag, bool,  EnableLoggingFalloutWarning),
-                           EWOMS_GET_PARAM(PreTypeTag, bool, EclStrictParsing),
+                           EWOMS_GET_PARAM(PreTypeTag, std::string, ParsingStrictness),
                            mpiRank,
                            EWOMS_GET_PARAM(PreTypeTag, int, EclOutputInterval),
                            cmdline_params,
@@ -626,7 +626,7 @@ private:
                   const std::string& outputMode,
                   const bool init_from_restart_file,
                   const bool allRanksDbgPrtLog,
-                  const bool strictParsing,
+                  const std::string& parsingStrictness,
                   const int mpiRank,
                   const int output_param,
                   const std::string& parameters,
diff --git a/opm/simulators/utils/readDeck.cpp b/opm/simulators/utils/readDeck.cpp
index e9d0b5825..bf12d0059 100644
--- a/opm/simulators/utils/readDeck.cpp
+++ b/opm/simulators/utils/readDeck.cpp
@@ -191,6 +191,7 @@ namespace {
                  const bool               checkDeck,
                  const Opm::Parser&       parser,
                  const Opm::ParseContext& parseContext,
+                 const bool               treatCriticalAsNonCritical,
                  Opm::ErrorGuard&         errorGuard)
     {
         Opm::Deck deck(parser.parseFile(deckFilename, parseContext, errorGuard));
@@ -203,7 +204,7 @@ namespace {
             Opm::KeywordValidation::specialValidation()
         };
 
-        keyword_validator.validateDeck(deck, parseContext, errorGuard);
+        keyword_validator.validateDeck(deck, parseContext, treatCriticalAsNonCritical, errorGuard);
 
         if (checkDeck) {
             Opm::checkDeck(deck, parser, parseContext, errorGuard);
@@ -235,6 +236,7 @@ namespace {
                       std::shared_ptr<Opm::Python>         python,
                       const bool                           initFromRestart,
                       const bool                           checkDeck,
+                      const bool                           treatCriticalAsNonCritical,
                       const std::optional<int>&            outputInterval,
                       Opm::ErrorGuard&                     errorGuard)
     {
@@ -248,7 +250,7 @@ namespace {
 
         auto parser = Opm::Parser{};
         const auto deck = readDeckFile(deckFilename, checkDeck, parser,
-                                       *parseContext, errorGuard);
+                                       *parseContext, treatCriticalAsNonCritical, errorGuard);
 
         if (eclipseState == nullptr) {
             eclipseState = createEclipseState(comm, deck);
@@ -490,7 +492,7 @@ void Opm::readDeck(Opm::Parallel::Communication    comm,
                    std::unique_ptr<WellTestState>& wtestState,
                    std::shared_ptr<SummaryConfig>& summaryConfig,
                    std::shared_ptr<Python>         python,
-                   const bool                      strictParsing,
+                   const std::string&              parsingStrictness,
                    const bool                      initFromRestart,
                    const bool                      checkDeck,
                    const std::optional<int>&       outputInterval)
@@ -500,13 +502,20 @@ void Opm::readDeck(Opm::Parallel::Communication    comm,
     int parseSuccess = 1; // > 0 is success
     std::string failureMessage;
 
+    if (parsingStrictness != "high" && parsingStrictness != "normal" && parsingStrictness != "low") {
+        OPM_THROW(std::runtime_error,
+                  fmt::format("Incorrect value {} for parameter ParsingStrictness, must be 'high', 'normal', or 'low'", parsingStrictness));
+    }
+
     if (comm.rank() == 0) { // Always true when !HAVE_MPI
+        const bool exitOnAllErrors = (parsingStrictness == "high");
+        const bool treatCriticalAsNonCritical = (parsingStrictness == "low");
         try {
-            auto parseContext = setupParseContext(strictParsing);
+            auto parseContext = setupParseContext(exitOnAllErrors);
             readOnIORank(comm, deckFilename, parseContext.get(),
                          eclipseState, schedule, udqState, actionState, wtestState,
                          summaryConfig, std::move(python), initFromRestart,
-                         checkDeck, outputInterval, *errorGuard);
+                         checkDeck, treatCriticalAsNonCritical, outputInterval, *errorGuard);
         }
         catch (const OpmInputError& input_error) {
             failureMessage = input_error.what();
diff --git a/opm/simulators/utils/readDeck.hpp b/opm/simulators/utils/readDeck.hpp
index 189069fc8..3ee94d904 100644
--- a/opm/simulators/utils/readDeck.hpp
+++ b/opm/simulators/utils/readDeck.hpp
@@ -60,7 +60,7 @@ enum class FileOutputMode {
 void
 ensureOutputDirExists(const std::string& cmdline_output_dir);
 
-std::unique_ptr<ParseContext> setupParseContext(const bool strictParsing);
+std::unique_ptr<ParseContext> setupParseContext(const bool exitOnAllErrors);
 
 // Setup the OpmLog backends
 FileOutputMode
@@ -85,7 +85,7 @@ void readDeck(Parallel::Communication         comm,
               std::unique_ptr<WellTestState>& wtestState,
               std::shared_ptr<SummaryConfig>& summaryConfig,
               std::shared_ptr<Python>         python,
-              bool                            strictParsing,
+              const std::string&              parsingStrictness,
               bool                            initFromRestart,
               bool                            checkDeck,
               const std::optional<int>&       outputInterval);
diff --git a/tests/test_keyword_validator.cpp b/tests/test_keyword_validator.cpp
index dc6468a22..feeaa6b32 100644
--- a/tests/test_keyword_validator.cpp
+++ b/tests/test_keyword_validator.cpp
@@ -277,7 +277,7 @@ ECHO
     KeywordValidator validator(test_unsupported_keywords, test_string_items, test_int_items, test_double_items, {});
     std::vector<ValidationError> errors;
     validator.validateDeckKeyword(test_keyword, errors);
-    const auto report = get_error_report(errors, false);
+    const auto report = get_error_report(errors, true, false);
     BOOST_CHECK(report
                 == "Unsupported keywords or keyword items:\n\n"
                    "  ECHO: keyword not supported\n"
@@ -296,7 +296,7 @@ ECHO
     KeywordValidator validator(test_unsupported_keywords, test_string_items, test_int_items, test_double_items, {});
     std::vector<ValidationError> errors;
     validator.validateDeckKeyword(test_keyword, errors);
-    const auto report = get_error_report(errors, true);
+    const auto report = get_error_report(errors, false, true);
     BOOST_CHECK(report.empty());
 }
 
@@ -311,7 +311,7 @@ NOECHO
     KeywordValidator validator(test_unsupported_keywords, test_string_items, test_int_items, test_double_items, {});
     std::vector<ValidationError> errors;
     validator.validateDeckKeyword(test_keyword, errors);
-    const auto report = get_error_report(errors, true);
+    const auto report = get_error_report(errors, false, true);
     BOOST_CHECK(report
                 == "Unsupported keywords or keyword items:\n\n"
                    "  NOECHO: keyword not supported\n"
@@ -329,7 +329,7 @@ NOECHO
     KeywordValidator validator(test_unsupported_keywords, test_string_items, test_int_items, test_double_items, {});
     std::vector<ValidationError> errors;
     validator.validateDeckKeyword(test_keyword, errors);
-    const auto report = get_error_report(errors, false);
+    const auto report = get_error_report(errors, true, false);
     BOOST_CHECK(report.empty());
 }
 
@@ -345,7 +345,7 @@ PINCH
     KeywordValidator validator(test_unsupported_keywords, test_string_items, test_int_items, test_double_items, {});
     std::vector<ValidationError> errors;
     validator.validateDeckKeyword(test_keyword, errors);
-    const auto report = get_error_report(errors, false);
+    const auto report = get_error_report(errors, true, false);
     BOOST_CHECK(report
                 == "Unsupported keywords or keyword items:\n\n"
                    "  PINCH: invalid value 'FOO' for item 2\n"
@@ -368,7 +368,7 @@ COMPDAT
     KeywordValidator validator(test_unsupported_keywords, test_string_items, test_int_items, test_double_items, {});
     std::vector<ValidationError> errors;
     validator.validateDeckKeyword(test_keyword, errors);
-    const auto report = get_error_report(errors, false);
+    const auto report = get_error_report(errors, true, false);
     BOOST_CHECK(report
                 == "Unsupported keywords or keyword items:\n\n"
                    "  COMPDAT: invalid value '0' in record 1 for item 2\n"
@@ -389,7 +389,7 @@ PINCH
     KeywordValidator validator(test_unsupported_keywords, test_string_items, test_int_items, test_double_items, {});
     std::vector<ValidationError> errors;
     validator.validateDeckKeyword(test_keyword, errors);
-    const auto report = get_error_report(errors, true);
+    const auto report = get_error_report(errors, false, true);
     BOOST_CHECK(report.empty());
 }
 
@@ -405,7 +405,7 @@ ENDSCALE
     KeywordValidator validator(test_unsupported_keywords, test_string_items, test_int_items, test_double_items, {});
     std::vector<ValidationError> errors;
     validator.validateDeckKeyword(test_keyword, errors);
-    const auto report = get_error_report(errors, false);
+    const auto report = get_error_report(errors, true, false);
     BOOST_CHECK(report
                 == "Unsupported keywords or keyword items:\n\n"
                    "  ENDSCALE: invalid value '0' for item 3\n"
@@ -424,7 +424,7 @@ ENDSCALE
     KeywordValidator validator(test_unsupported_keywords, test_string_items, test_int_items, test_double_items, {});
     std::vector<ValidationError> errors;
     validator.validateDeckKeyword(test_keyword, errors);
-    const auto report = get_error_report(errors, true);
+    const auto report = get_error_report(errors, false, true);
     BOOST_CHECK(report.empty());
 }
 
@@ -440,7 +440,7 @@ ENDSCALE
     KeywordValidator validator(test_unsupported_keywords, test_string_items, test_int_items, test_double_items, {});
     std::vector<ValidationError> errors;
     validator.validateDeckKeyword(test_keyword, errors);
-    const auto report = get_error_report(errors, true);
+    const auto report = get_error_report(errors, false, true);
     BOOST_CHECK(report
                 == "Unsupported keywords or keyword items:\n\n"
                    "  ENDSCALE: invalid value '0' for item 4\n"
@@ -459,7 +459,7 @@ ENDSCALE
     KeywordValidator validator(test_unsupported_keywords, test_string_items, test_int_items, test_double_items, {});
     std::vector<ValidationError> errors;
     validator.validateDeckKeyword(test_keyword, errors);
-    const auto report = get_error_report(errors, false);
+    const auto report = get_error_report(errors, true, false);
     BOOST_CHECK(report.empty());
 }
 
@@ -485,7 +485,7 @@ ENDSCALE
     validator.validateDeckKeyword(test_keyword2, errors);
     validator.validateDeckKeyword(test_keyword3, errors);
     validator.validateDeckKeyword(test_keyword4, errors);
-    const auto report = get_error_report(errors, false);
+    const auto report = get_error_report(errors, true, false);
     BOOST_CHECK(report
                 == "Unsupported keywords or keyword items:\n\n"
                    "  ECHO: keyword not supported\n"
@@ -516,7 +516,7 @@ ENDSCALE
     validator.validateDeckKeyword(test_keyword2, errors);
     validator.validateDeckKeyword(test_keyword3, errors);
     validator.validateDeckKeyword(test_keyword4, errors);
-    const auto report = get_error_report(errors, true);
+    const auto report = get_error_report(errors, false, true);
     BOOST_CHECK(report
                 == "Unsupported keywords or keyword items:\n\n"
                    "  NOECHO: keyword not supported\n"