That last claim resulted in convictions for holocaust denial in both France and Germany. When added to a string of indictments for inciting racial hatred, it has effectively made it impossible for France’s mainstream right-of-centre parties to contemplate an alliance with a group whose views on race, immigration and Europe appeared to be shared by around one in six of French voters.

Regrets? Le Pen says not.

“It is they [the mainstream right] who should have regrets because they have been the principal victims of this suicidal policy,” the veteran leader told AFP in an interview to mark Friday’s anniversary.

“By refusing an alliance with the FN they have condemned themselves to losing all power. You should ask them how they can justify this suicidal attitude.”

Le Pen, who attributes the orthodox right’s reluctance to deal with the FN to the alleged influence of Jewish organisation B’nai B’rith, says he cannot understand why his “detail” comment continues to represent a barrier to rapprochement across the spectrum of right-wing parties in France.

“This is sufficient to justify that political parties prefer to commit suicide rather than ally themselves to the man who said that?” he asked.

“It is like saying the gas chambers have a fundamental, huge, undeniable importance in French politics.”

Although he has handed over the leadership of the party to his daughter Marine, who polled 17.9 per cent in the first round of his year’s presidential election and has been credited with giving the FN a more respectable, voter-friendly public face, Le Pen remains an influential figure behind the scenes.

From the party’s birth, he has been its dominant figure, quickly establishing himself as the undisputed leader and eventually ousting the remnants of the Ordre Nouveau group of street-fighting neo-fascists who were one of the significant constituent parts of the new party founded in 1972.

The party was to remain restricted to the fringes of French politics for the next decade before a breakthrough in municipal elections in 1983 saw it emerge as the significant force it has remained to this day.

The party’s electoral highpoint arguably came in 2002, when Le Pen outscored the Socialist Lionel Jospin to advance to the second-round run-off in the presidential election.

That success however also underlined the limits of the Front’s potential. Their leader suffered a crushing defeat at the hands of Jacques Chirac and the party subsequently failed to secure a single seat in parliament in legislative elections the same year.

Gilles Ivaldi, a researcher at the state-financed think-tank CNRS, says the FN has a unique position in the European political landscape.

“It is held at arm’s length from power but it retains a formidable power to influence the political debate, as the this year presidential campaign showed,” he argues.

“With [ex-president] Nicolas Sarkozy talking about the failure of multiculturalism or there being too many foreigners in France, the FN’s ideas were at the heart of the debate.”

Terra Nova, a study group that is close to the ruling Socialists, warned earlier this year that ideological convergence between the mainstream right and the FN would sooner or later lead to the creation of a broad right-wing alliance of ‘patriots’ that the French left would find difficult to beat.

But other political experts disagree. They argue that the FN is likely to prove incapable of abandoning the policies that define it, but which also place it beyond the pale for the mainstream right.

As Gilles Ivaldi underlines, attempting to curb immigration by banning immigrants from bringing their families to France would require the country to renounce a series of international human rights conventions.

“Marine Le Pen is effectively in a political no man’s land,” Ivaldi argues.

“She’s free to say what she wants and to polarise political debate, but if she really wants to obtain power, she will have to deradicalise her stances and if she does that the risk is she loses her appeal.”