France's far-right National Front (FN) party has denounced a police search of its headquarters as a media stunt.
It comes amid an investigation into the alleged misappropriation of European Union funds.
But the FN vice-president said the "system is in a panic" as polls gave leader Marine Le Pen a strong showing in the upcoming presidential election.
Ms Le Pen has meanwhile walked out of a meeting with the leading Muslim cleric in Lebanon in a row over a headscarf.
On a visit to Lebanon, she refused to wear a headscarf for the meeting with Grand Sunni Muslim Mufti, Sheikh Abdel-Latif Derian, telling reporters she would "not cover myself up".
However, the mufti's press office said that Ms Le Pen's aides had been informed beforehand of their requirement for her to wear a head covering.
Correspondents say Ms Le Pen is trying to burnish her foreign policy credentials with her trip.
A central plank of Ms Le Pen's campaign is her opposition to what she says is the imposition of Islamic customs on French culture.
The raid on the FN's headquarters came after the European Parliament, of which Ms Le Pen is a member, accused her of defrauding it of nearly €340,000 (£288,000; $358,000) to illegally pay for aides rather than parliamentary assistants.
On Friday, a leaked report from the EU's anti-fraud office, Olaf, said the parliament had paid €41,554 towards a three-month contract for Ms Le Pen's bodyguard Thierry Legier - who was falsely presented as a parliamentary assistant. It said Ms Le Pen had herself admitted that the money was used for other expenses.
Ms Le Pen vehemently denied the claim.
Police raided the FN headquarters outside Paris on Monday night, reportedly taking copies of computer hard drives as part of the investigation.
In a statement, the FN said this search proved that another last February had "amounted to nothing". It accused investigators of conducting a "media operation whose sole purpose is to try to disrupt the smooth running of the presidential election campaign".
An Opinionway survey on Monday put Ms Le Pen on 27% for the first round of the presidential election in April - seven percentage points ahead of her two closest rivals, Emmanuel Macron and Francois Fillon.
The poll, and another recent poll with similar findings, still suggest she would lose in the two-way second round in May - but the gap is closing.