French presidential candidate Francois Fillon faced mounting pressure from his own conservative camp to withdraw from the race on Saturday, as a senator from The Republicans party warned it could split if he refused to bow out.

Senator Bruno Gilles, head of the party's influential Bouches-du-Rhone region, said in a radio interview that party faithful had "turned the page" and overwhelmingly wanted a change of candidate.

Fillon, 62, has been embroiled in a deepening scandal since satirical newspaper Le Canard Enchaine reported he had paid his wife hundreds of thousands of euros of public money for work she may not have done.

He has steadfastly maintained that his wife Penelope had contributed real work as his assistant, but the allegations to the contrary and the sums involved have rocked his campaign.

The former front-runner is now set to place third behind far-right leader Marine Le Pen and independent Emmanuel Macron in the election's first round on April 23, according to the latest major poll of voting intentions.

"This scandal is doing us more damage every day, and we can't wait another two weeks," Gilles told France Bleu Provence radio. "There are presidential and legislative elections at stake and, beyond that, the survival of our political party."

The senator added: "This could go as far as a party split."

According to a new opinion poll for the Journal du Dimanche, the proportion of French voters who believe Fillon to be "honest" has plummeted to 23 percent from 50 percent last November. Pollster Ifop surveyed 1,007 people from Feb. 3-4.

But Fillon, a former prime minister, has vowed to fight on, defying public calls from a growing number of Republican lawmakers and officials for him to step aside.

On Saturday his campaign distributed 3 million leaflets entitled "Stop the Manhunt", characterising the scandal as a left-wing conspiracy and declaring: "Enough is enough".