More than a dozen European Union nations have failed to fully criminalize the denial of crimes against humanity and war crimes, the EU's executive said on Holocaust Remembrance Day.

Though the bloc agreed in 2008 to outlaw the denial, condonement or gross trivialization of such crimes, around half of its 28 members have failed to write these rules into their domestic legislation, the European Commission said.

"Today, we have achieved peace between nations in the European Union," said the bloc's Justice Commissioner Viviane Reding.

"Yet another challenge remains: to continue the quest for tolerance. Nobody should ever have to experience hate speech or hate crime."

Reding said she was urging all EU states to swiftly transpose EU rules into their national laws.

Countries not in line with the 2008 rules by December 1 this year could face judicial action.

The Commission said 13 countries -- Austria, Belgium, Britain, Czech Republic, Denmark, Germany, Estonia, Finland, Greece, Ireland, Hungary, the Netherlands and Sweden -- have no criminal law provisions governing the public condoning, denial and gross trivialization of genocide, crimes against humanity and war crimes.

And 15 nations -- Bulgaria, Britain, Croatia, Denmark, Estonia, Finland, Greece, Ireland, Italy, Latvia, Malta, the Netherlands, Portugal, Spain and Sweden -- have no specific provisions criminalizing public condoning, denial and gross trivialization of crimes against peace, war crimes and crimes against humanity by major war criminals of the European Axis countries.

In a separate statement, EU foreign policy chief Catherine Ashton said Holocaust Remembrance Day was an occasion "to remind us all of the need to continue fighting prejudice and racism in our own time."

"We must remain vigilant against the dangers of hate speech and redouble our commitment to prevent any form of intolerance," she added.

Anti-immigration sentiment is on the rise across Europe, with extremist rightwing parties looking to make strong gains in elections for the European Parliament in May.