Le Pen, who is one of the frontrunners in the race, told French news agency 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. During this period, there cannot be the neutrality or calm necessary for the justice system to function properly."
The candidate's lawyer 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.
Le Pen, who sits in the European Parliament, denies 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 has vowed to call a referendum on France's membership of the European Union if elected and 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.
- with AFP