The party top brass had gathered in Paris to review its dismal performance in Sunday's European elections, but the spotlight swung on the latest scandal after Sarkozy's former deputy campaign director alleged more fraud.

Jerome Lavrilleux dropped a bombshell, claiming that bills for Sarkozy's failed 2012 re-election campaign were passed off as invoices for party conferences.

Although Lavrilleux said they were "anomalies" and claimed that neither Sarkozy nor Cope were in the loop, the latest saga in the so-called Bygmalion scandal was a further blow to the party, which suffered its first ever defeat to the far-right National Front at the European elections.

Event & Cie, a subsidiary of the Bygmalion PR company owned by Cope's friends, reportedly overbilled the UMP, earning at least €8 million (HK$84.5 million) to organise rallies.

Just hours before Lavrilleux's dramatic claim, a lawyer for Bygmalion said the company had been pressured to falsify Sarkozy's bills or risk not getting paid.

Sarkozy, who has been implicated in several corruption scandals and denies any wrongdoing, is "very unhappy to see his name dragged into this strange affair", his close ally and former minister Brice Hortefeux said.

Sarkozy has faced accusations he tried to pervert the course of justice and that late Libyan leader Muammar Gaddafi financed part of his successful 2007 election campaign.

France's constitutional court rapped Sarkozy last year for exceeding campaign spending limits and the party plunged into debt following its defeat in the 2012 legislative elections.