diff --git a/python/core/processing/qgsprocessingutils.sip b/python/core/processing/qgsprocessingutils.sip
index 287008c555ec..71fd7ec46525 100644
--- a/python/core/processing/qgsprocessingutils.sip
+++ b/python/core/processing/qgsprocessingutils.sip
@@ -86,15 +86,6 @@ class QgsProcessingUtils
  :rtype: str
 %End
 
-    static QList< QVariant > uniqueValues( QgsVectorLayer *layer, int fieldIndex, const QgsProcessingContext &context );
-%Docstring
- Returns a list of unique values contained in a single field in a ``layer``, when
- the settings from the supplied ``context`` are respected. E.g. if the
- context is set to only use selected features, then calling this will
- return unique values from selected features in the layer.
- :rtype: list of QVariant
-%End
-
 
     static void createFeatureSinkPython(
       QgsFeatureSink **sink /Out,TransferBack/,
diff --git a/src/core/processing/qgsprocessingutils.cpp b/src/core/processing/qgsprocessingutils.cpp
index e1692551c12f..e5ee667993e6 100644
--- a/src/core/processing/qgsprocessingutils.cpp
+++ b/src/core/processing/qgsprocessingutils.cpp
@@ -226,36 +226,6 @@ QString QgsProcessingUtils::normalizeLayerSource( const QString &source )
   return normalized.trimmed();
 }
 
-
-QList<QVariant> QgsProcessingUtils::uniqueValues( QgsVectorLayer *layer, int fieldIndex, const QgsProcessingContext &context )
-{
-  if ( !layer )
-    return QList<QVariant>();
-
-  if ( fieldIndex < 0 || fieldIndex >= layer->fields().count() )
-    return QList<QVariant>();
-
-  bool useSelection = context.flags() & QgsProcessingContext::UseSelectionIfPresent && layer->selectedFeatureCount() > 0;
-  if ( !useSelection )
-  {
-    // not using selection, so use provider optimised version
-    QSet<QVariant> values = layer->uniqueValues( fieldIndex );
-    return values.toList();
-  }
-  else
-  {
-    // using selection, so we have to iterate through selected features
-    QSet<QVariant> values;
-    QgsFeature f;
-    QgsFeatureIterator it = layer->getSelectedFeatures( QgsFeatureRequest().setSubsetOfAttributes( QgsAttributeList() << fieldIndex ).setFlags( QgsFeatureRequest::NoGeometry ) );
-    while ( it.nextFeature( f ) )
-    {
-      values.insert( f.attribute( fieldIndex ) );
-    }
-    return values.toList();
-  }
-}
-
 void parseDestinationString( QString &destination, QString &providerKey, QString &uri, QString &format, QMap<QString, QVariant> &options )
 {
   QRegularExpression splitRx( "^(.*?):(.*)$" );
diff --git a/src/core/processing/qgsprocessingutils.h b/src/core/processing/qgsprocessingutils.h
index 3db5618d994c..660662ddbe8e 100644
--- a/src/core/processing/qgsprocessingutils.h
+++ b/src/core/processing/qgsprocessingutils.h
@@ -99,14 +99,6 @@ class CORE_EXPORT QgsProcessingUtils
      */
     static QString normalizeLayerSource( const QString &source );
 
-    /**
-     * Returns a list of unique values contained in a single field in a \a layer, when
-     * the settings from the supplied \a context are respected. E.g. if the
-     * context is set to only use selected features, then calling this will
-     * return unique values from selected features in the layer.
-     */
-    static QList< QVariant > uniqueValues( QgsVectorLayer *layer, int fieldIndex, const QgsProcessingContext &context );
-
     /**
      * Creates a feature sink ready for adding features. The \a destination specifies a destination
      * URI for the resultant layer. It may be updated in place to reflect the actual destination
diff --git a/tests/src/core/testqgsprocessing.cpp b/tests/src/core/testqgsprocessing.cpp
index 60c85b66900b..bb89820f3457 100644
--- a/tests/src/core/testqgsprocessing.cpp
+++ b/tests/src/core/testqgsprocessing.cpp
@@ -789,20 +789,27 @@ void TestQgsProcessing::uniqueValues()
   QgsProcessingContext context;
   context.setFlags( QgsProcessingContext::Flags( 0 ) );
 
+  QgsProject p;
+  p.addMapLayer( layer );
+  context.setProject( &p );
+
+  QgsProcessingParameterDefinition *def = new QgsProcessingParameterString( QStringLiteral( "string" ) );
+  QVariantMap params;
+  params.insert( QStringLiteral( "string" ), layer->id() );
+
+  std::unique_ptr< QgsFeatureSource > source( QgsProcessingParameters::parameterAsSource( def, params, context ) );
+
   // some bad checks
-  QVERIFY( QgsProcessingUtils::uniqueValues( nullptr, 0, context ).isEmpty() );
-  QVERIFY( QgsProcessingUtils::uniqueValues( nullptr, -1, context ).isEmpty() );
-  QVERIFY( QgsProcessingUtils::uniqueValues( nullptr, 10001, context ).isEmpty() );
-  QVERIFY( QgsProcessingUtils::uniqueValues( layer, -1, context ).isEmpty() );
-  QVERIFY( QgsProcessingUtils::uniqueValues( layer, 10001, context ).isEmpty() );
+  QVERIFY( source->uniqueValues( -1 ).isEmpty() );
+  QVERIFY( source->uniqueValues( 10001 ).isEmpty() );
 
   // good checks
-  QList< QVariant > vals = QgsProcessingUtils::uniqueValues( layer, 0, context );
+  QSet< QVariant > vals = source->uniqueValues( 0 );
   QCOMPARE( vals.count(), 3 );
   QVERIFY( vals.contains( 1 ) );
   QVERIFY( vals.contains( 2 ) );
   QVERIFY( vals.contains( 3 ) );
-  vals = QgsProcessingUtils::uniqueValues( layer, 1, context );
+  vals = source->uniqueValues( 1 );
   QCOMPARE( vals.count(), 3 );
   QVERIFY( vals.contains( QString( "A" ) ) );
   QVERIFY( vals.contains( QString( "B" ) ) );
@@ -811,12 +818,13 @@ void TestQgsProcessing::uniqueValues()
   //using only selected features
   layer->selectByIds( QgsFeatureIds() << 1 << 2 << 4 );
   // but not using selection yet...
-  vals = QgsProcessingUtils::uniqueValues( layer, 0, context );
+  source.reset( QgsProcessingParameters::parameterAsSource( def, params, context ) );
+  vals = source->uniqueValues( 0 );
   QCOMPARE( vals.count(), 3 );
   QVERIFY( vals.contains( 1 ) );
   QVERIFY( vals.contains( 2 ) );
   QVERIFY( vals.contains( 3 ) );
-  vals = QgsProcessingUtils::uniqueValues( layer, 1, context );
+  vals = source->uniqueValues( 1 );
   QCOMPARE( vals.count(), 3 );
   QVERIFY( vals.contains( QString( "A" ) ) );
   QVERIFY( vals.contains( QString( "B" ) ) );
@@ -824,18 +832,17 @@ void TestQgsProcessing::uniqueValues()
 
   // selection and using selection
   context.setFlags( QgsProcessingContext::UseSelectionIfPresent );
-  QVERIFY( QgsProcessingUtils::uniqueValues( layer, -1, context ).isEmpty() );
-  QVERIFY( QgsProcessingUtils::uniqueValues( layer, 10001, context ).isEmpty() );
-  vals = QgsProcessingUtils::uniqueValues( layer, 0, context );
+  source.reset( QgsProcessingParameters::parameterAsSource( def, params, context ) );
+  QVERIFY( source->uniqueValues( -1 ).isEmpty() );
+  QVERIFY( source->uniqueValues( 10001 ).isEmpty() );
+  vals = source->uniqueValues( 0 );
   QCOMPARE( vals.count(), 2 );
   QVERIFY( vals.contains( 1 ) );
   QVERIFY( vals.contains( 2 ) );
-  vals = QgsProcessingUtils::uniqueValues( layer, 1, context );
+  vals = source->uniqueValues( 1 );
   QCOMPARE( vals.count(), 2 );
   QVERIFY( vals.contains( QString( "A" ) ) );
   QVERIFY( vals.contains( QString( "B" ) ) );
-
-  delete layer;
 }
 
 void TestQgsProcessing::createIndex()