French far-right Front National party president Marine Le Pen | Marin Bureau/AFP via Getty Images Marine Le Pen’s party under investigation for fraud Paris prosecutor’s office opens case against National Front for misuse of funds in Brussels.

Authorities in Paris have opened an investigation into the far-right National Front over suspected fraud linked to the misuse of assistants at the European Parliament.

The case, launched by prosecutors last month, will investigate suspected "fraud," "conspiracy to commit fraud," "dissimulated labor" and other charges against the party, according to leaked documents seen by Le Monde.

The party has faced scrutiny on the issue for more than two years, both in France and in Brussels.

The European Parliament is seeking to recover €339,000 from party chief Marine Le Pen as part of an investigation conducted by OLAF, Europe's anti-fraud watchdog, into alleged misuse of funds.

Le Pen is accused of breaking the Parliament’s rules by having two assistants — Thierry Légier and Catherine Griset — carry out non-parliamentary work while being paid by the EU institution.

The financial penalties against Le Pen echo those imposed on her father, Jean-Marie Le Pen. The former chief of the National Front, who is also an MEP, was in June accused of misusing resources and ordered to repay €320,000.

In France, party treasurer Wallerand de Saint-Just is under formal investigation over alleged campaign finance fraud. The party is accused of having willingly inflated the price of campaign kits sold to election candidates in 2012 in order to boost the amount of money it could reclaim from the French state.

A lawyer from the National Front was not immediately available for comment.