Member of parliament Jean-Luc Melenchon of La France Insoumise (France Unbowed) political party attends the traditional Bastille Day military parade on the Champs-Elysees in Paris, France, July 14, 2017. REUTERS/Gonzalo Fuentes

PARIS (Reuters) - An investigation into alleged misuse of European parliamentary funds by members of a number of French political parties has been extended to include far-left leader Jean-Luc Melenchon, a judicial source said on Tuesday.

The preliminary investigation - already targeting members of France’s centrist MoDem party, conservative party The Republicans, and the Socialist party - was opened after a member of Marine Le Pen’s far-right National Front asked the Paris prosecutor to look into the issue.

Le Pen is herself under formal investigation for breach of trust in a separate case on the same subject.

According to Le Parisien daily newspaper, three people who were Melenchon’s parliamentary aides while he was a member of the European Parliament from 2009 to 2017, are to be investigated.

Being a target of a preliminary investigation or a formal investigation in France does not necessarily lead to a trial.

Melenchon, now a member of the French parliament, leader of the France Unbowed party and a vocal opponent of the government of centrist Emmanuel Macron, denied any misconduct in a weekly briefing on Tuesday afternoon.

Political probity became a major issue during this year’s presidential campaign in which Le Pen and Melenchon were both high-scoring candidates, eventually losing to centrist Emmanuel Macron.