Copy of fake leaflet portraying Jean-Luc Melenchon's political platform (Screengrab)

Supporters of France's far-right Front National (FN) party, led by Marine Le Pen, have been caught distributing fake pamphlets in Arabic to smear her far-left opponent, Jean-Luc Melenchon, in the run-up to parliamentary elections.

The fake leaflet had a picture of the politician along with the slogan "Let's vote Melenchon" in approximate Arabic - written from left to right instead of right to left.

Melenchon and Le Pen are both campaigning for the same constituency, Henin-Beaumont, in the north of France, ahead of parliamentary elections this month.

"It's fake propaganda and it could cost her the election because it's illegal to distribute fake pamphlets in France," said the Front Left (FG) leader.

The leaflets also contained a quote: "There is no future for France without the Arabs and Berbers of North Africa" taken from a political meeting held by Melenchon in Marseille.

The FN initially denied being responsible for the leaflets, attributing them to friends of the party.

Le Pen later recanted and admitted distributing the leaflets. "I take responsibility for the pamphlet," Le Pen said on the French TV channel Canal Plus. "It's not unfair, I was simply quoting him," she added.

Le Pen and Melenchon previously competed against each other in the presidential elections this year.

In the first round, Melenchon scored lower than the polls predicted with 11.1 percent, against 17.9 percent for Le Pen.

After neither of them won, Melenchon chose to challenge Le Pen directly by challenging her for her constituency - the deindustrialised Nord-Pas-de-Calais region - in the parliamentary elections, instead of running in one of the areas where his party scored the highest.

The Nord-Pas-de-Calais has a high level of unemployment, after being harshly hit by the closure of its mines and other industries, and Le Pen's social programme was well received there during the first round of the presidential elections.

Melenchon has often insulted Le Pen, calling her a "beast spitting hatred", a "bat", a "dark presence" and "half-demented".

No wonder the French media have termed the contest between them "Le Duel".