Two Le Monde reporters cite Jean-Pierre Jouyet as saying Fillon wanted the judicial probes into alleged misuse of UMP party funds in Sarkozy’s 2012 presidential election campaign speeded up.

Fillon’s instructions allegedly took place over a lunch with Jouyet in June.

When challenged, Jouyet denied having made the claims about Fillon, but he later recanted on Sunday (9 November) when the reporters said they had recordings of his comments.

"If you don't hit him [Sarkozy] quickly, you'll let him come back, so act," Fillon is alleged to have said, according to Jouyet.

Fillon, for his part, is suing the two journalists and Le Monde for libel. He is also threatening Jouyet with defamation and has called him a liar.

“If Monsieur Jouyet says that, it’s a lie,” he said on French television.

The revelations have sparked a nation-wide scandal, with Fillon set to face off his party rival Sarkozy in the 2017 presidential elections.

Despite the allegations, Sarkozy’s spokesperson on Monday rallied behind Fillon’s version of events and told French radio that Jouyet should step down.

"There's no reason not to believe Fillon," he said.

The spokesperson said Jouyet had given state secrets to journalists and described him as “careless”.

Meanwhile, the fallout between the two party rivals could be a gain for the Marine Le Pen and her far-right National Front party.

Her popularity has soared in recent months as Socialist president Hollande struggles to kick-start an ailing economy and create jobs.

The UMP in-fighting has also played into her hands, say political analysts.