PARIS (AP) — French authorities have stepped up their investigation into accusations that members of the far right National Front tricked the European Parliament out of several hundred thousand euros paid to legislative aides.

Party members are accused of using assistants for political activity even though they're on the parliament's payroll.

It's one of multiple investigations around the National Front or its finances that are casting a shadow over party leader Marine Le Pen's campaign for France's April-May presidential election.

The Paris prosecutor's office said Thursday that a judicial inquiry was opened last month into the use of parliamentary aides, on potential charges including fraud, abuse of trust and organized criminal activity.

Party treasurer Wallerand Saint Just said the accusations are unfounded and a "persecution" campaign aimed at hurting Le Pen's presidential bid.