“This is one of the persecutions targeting opposition politicians to silence or disqualify them with the help of politicians and organisations tasked with political inquisition at a time when a crucial debate begins or should begin on France’s survival,” he told reporters, referring to the upcoming referendum on the European Union’s first constitution.

Le Pen, the 76 year-old founder of the National Front (FN) party, is campaigning against approval of the EU constitution in the referendum that is set to take place sometime before the summer in France.

The EU constitution, signed by EU government leaders amid huge fanfare in Rome on October 30, faces a series of referendums in different countries which have chosen to put the constitution to a popular vote.

A “no” vote in any one could in theory block the treaty, which aims to speed up decision-making in the EU following its expansion to include 25 nations last May.

The investigation by the Paris prosecutor’s office was to focus on whether Le Pen’s comments, which were made to the extreme right-wing magazine Rivarol, constitute “denial of crimes against humanity” or “apology for war crimes” – both of which are criminal offences.

Le Pen caused outrage when he said that “in France at least the German occupation was not especially inhumane, even if there were a number of excesses – inevitable in a country of 550,000 square kilometres.”

“If the Germans had carried out mass executions across the country as the received wisdom would have it, then there wouldn’t have been any need for concentration camps for political deportees.

“It’s not just from the European Union and globalisation that we need to deliver our country, but also from the lies about its history,” he told the weekly.

The remarks drew immediate comparisons with Le Pen’s oft-quoted description of the Jewish holocaust as a “detail” of World War Two, and were universally condemned by Jewish and anti-racist groups, veterans’ organisations and political parties.

Le Pen defended himself Monday, saying: “I have always regarded the German army and police as enemy organisations which I judge without complacency while trying to be fair and to reject a manichean view of the world.”