Le Pen, who is one of the frontrunners in the race, told AFP she refused to be questioned by anti-corruption investigators during the presidential campaign.
“I will not respond (to the summons) during the election campaign,” she said.
“During this period, there cannot be the neutrality or calm necessary for the justice system to function properly.”
The candidate's lawyer Rodolphe Bosselut said he was surprised by the “sudden rush” in the investigation.
Le Pen's personal assistant Catherine Griset was charged on Wednesday with breach of trust in the probe into allegations that her National Front (FN) party defrauded the European Parliament of about 340,000 euros ($360,000).
Le Pen, who sits in the European Parliament, has furiously denied accusations she broke the rules by using parliamentary funds to pay Griset as well as bodyguard Thierry Legier for jobs in France rather than at the European Parliament.
Le Pen, who has vowed to call a referendum on France's membership of the European Union if elected, has described the investigation as a vendetta.
She is not the only presidential candidate facing accusations over 'fake jobs'. Her conservative rival Francois Fillon is fighting claims he paid his wife more than 700,000 euros for parliamentary work that she might not have carried out.
However while Fillon's popularity has been hit hard by the scandal analysts suggest that Le Pen's own supporters are unlikely to be turned off by the allegations the National Front broke EU rules.
For a start, and in contrast to Fillon, it does not appear Le Pen gained personally from the rule breaks and given her supporters are firmly anti-EU anyway, analysts suggest most of them will see little wrong in what the party has done.
Plus the investigations tie into her long-stated argument that her party has been the victim of a witch-hunt by the establishment and mainstream media.
Polls currently show Le Pen will finish with most votes in the first round of the presidential election on April 23 but would be beaten by either Fillon or centrist Emmanuel Macron in the runoff.