GETTY Marine Le Pen and Martin Schulz

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Mrs Le Pen condemned the investigation as politically motivated and deliberately timed to coincide with recent powerful performances in the opinion polls ahead of French elections. She has also accused investigators of showing double standards. The firebrand politician referred to a 2015 complaint she made against Herbert Hansen - a senior aide to then-European Parliament President Martin Schulz - who was cleared of wrongdoing after a 21-month investigation.

GETTY Firebrand French far-right leader Marine Le Pen is furious at an EU probe

A good illustration of these hate-filled, pathetic socialists who are so predictable across Europe Marine Le Pen

At the same time, OLAF was already involved in another investigation of Mrs Le Pen which concluded she violated European Parliament rules by having two of her assistants — Thierry Légier and Catherine Griset — carry out non-parliamentary work while on its payroll. Ms Le Pen was told to repay the Parliament £285,000, which she has yet to do. At the time she described Mr Schulz as “a good illustration of these hate-filled, pathetic socialists who are so predictable across Europe” and suggested he carried out his own inquiry into Mr Hansen. Mrs Le Pen’s lawyer Marcel Ceccaldi alleges that OLAF used 'double standards' when investigating the two cases. And she now claims OLAF acted as a tool of Mr Schulz to undermine her and her party and has filed a lawsuit against OLAF and its director-general, Giovanni Kessler.

GETTY Marine Le Pen and prominent Front National member Gilbert Collard

Mr Kessler insisted his agency was above the political fray and said the same methods had been used to investigate the claims about Mr Hansen as those about Mrs Le Pen’s assistants. He told politico.eu: “OLAF has conducted thorough, objective and independent investigations, revealing documented evidence. “While we used the same investigative methods, principles and tools in both cases, the investigations revealed very different facts.

GETTY Marine Le Pen is flying high in the opinion polls

Things you didn't know about Marine Le Pen Fri, May 5, 2017 Marine Le Pen is a French politician who is the president of the National Front, a national-conservative political party in France and one of its main political forces. Play slideshow AFP/Getty Images 1 of 10 Described as more democratic and republican than her nationalist father, she has led a movement of "de-demonization of the Front National" to detoxify it and soften its image