French far-right leader Marine Le Pen allegedly used fake job contracts for two of her assistants in the European Parliament, according to a report by the EU anti-fraud body, Olaf.

A three-month contract, signed in October 2011 by Le Pen for Thierry Legier, her bodyguard, could constitute a "misappropriation of funds, or fraud and use of fraud", the European Anti-Fraud Office (Olaf) said in a report handed to French judges last year and revealed by French media on Thursday (16 February).

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It said the contract did not correspond to reality and pointed out that Legier's salary - €7,237 net per month for a part-time post - was "extremely high".

According to the report, leaked by the Mediapart news website and by Marianne, a weekly, Le Pen admitted to Olaf investigators that she had "not employed Legier during these three months".

She said the job contract had been established to "rectify earlier salaries and charges spending that has not been paid by the parliament".

Olaf also said that another person paid since December 2010 as an EU parliament assistant to Le Pen, Catherine Griset, was actually her personal assistant at the National Front's headquarters in France.

The anti-fraud office started to investigate in June 2014 on suspicions of violations of the parliament's rules and "possible use of fake jobs" by Le Pen since 2009.

It could not confirm allegations that Louis Aliot, Le Pen's partner and now an MEP, and Florian Philippot, also an MEP and the FN's deputy leader, were unduly paid as assistants to Le Pen before their election in 2014.

But it said the cost to the parliament of Legier and Griset's alleged fake contracts amounted to €336,146.

The parliament was due to start recovering the money this month, to be taken from Le Pen's salary as an MEP.

Le Pen's laywer said that Olaf's accusations were "balderdash".

Last month Le Pen said she would not repay the parliament and said that the investigation was "persecution, a unilateral decision taken by political opponents".

French judges opened a case in December over embezzlement, organised fraud, forgery, and undeclared work against the FN, following a preliminary investigation that was opened in March 2015 at the request of European Parliament president Martin Schulz.

The publication of Olaf's report comes as Le Pen benefits from similar accusations against centre-right presidential candidate Francois Fillon, who employed his wife and children as parliamentary assistants in France.

In the most recent poll ahead of April's first round of the presidential election, Le Pen leads with 26 percent, while Fillon is down 13 percent to 18.5 percent. Fillon is now third in the race behind the liberal-left candidate Emmanuel Macron, with 23 percent.

Until now, no poll has said Le Pen would win the election in the second round, but with Fillon in difficulty the possibility is more likely.