French presidential candidate Marine Le Pen has refused a police interview about her alleged misuse of EU funds.
The far-right leader denies wrongdoing and claims that the allegations are a plot to derail her campaign.
On Wednesday, Ms Le Pen's aide Catherine Griset was placed under police investigation over the payments.
The European Parliament alleges that more than €300,000 (£257,000; $321,000) of its funding was misspent by Ms Le Pen's National Front (FN) party.
"I will not respond [to the summons] during the election campaign," said Ms Le Pen on Friday.
"During this period, there cannot be the neutrality or calm necessary for the justice system to function properly," she added.
As a European member of parliament, Ms Le Penn was allocated the money for costs, on condition that the work was carried out in Brussels or Strasbourg.
However, it is alleged the money was largely used to pay the salary of Ms Griset, who is said to have spent most of her time at the FN headquarters in Paris.
Ms Griset is a close friend of Ms Le Pen as well as her cabinet director. Ms Le Pen's bodyguard, Thierry Legier, was also detained on Wednesday, but later released.
A deadline to repay the money elapsed at the end of January.
Ms Le Pen said then that she had no intention of complying, and as a European member of parliament police cannot force her into questioning.
She has repeatedly claimed that she is a victim of a politically-motivated vendetta.
The BBC's Paris correspondent, Hugh Schofield, said Ms Le Pen's enemies hope the scandal will damage her reputation, but so far there is little sign of that, partly because there is no allegation of personal enrichment in the affair.
Ms Le Pen is one of the front-runners in the French presidential election to be held in April and May. If she wins, she has promised a Brexit-style referendum on France's membership of the EU.
Polls suggest that she will make it to the run-off where she is likely to face conservative candidate Francois Fillon or centrist Emmanuel Macron.