Jean-Marie Le Pen, photographed in his house in June this year. Photo: Christophe Archambault/AFP
Le Pen, who was an MEP from the 1980s up until this year, was investigated over the improper spending of EU funds after the European Parliament lifted his immunity in March.
Judges questioned Le Pen for more than four hours about the jobs of three of his aides, according to his lawyers.
Le Pen, 91, “is very tired of all this,” said lawyer Frederic Joachim, condemning the case as an “incursion of the judiciary into the legislature”.
Le Pen had used his parliamentary immunity to prevent anti-corruption investigators from questioning him in June last year about the case.
Despite losing his immunity, Le Pen has refused to appear before the judges. Le Pen's estranged daughter Marine, who now heads the renamed National Rally, has already been charged in the case.
Investigators suspect the National Front used money from Brussels earmarked for parliamentary assistants there to pay staff for party work in France.
It is estimated almost seven million euros was diverted from the European Parliament between 2009 and 2017.