French conservative presidential candidate Francois Fillon, embroiled in a scandal involving salaries paid to his wife for work she may not have done, would not get through to the runoff vote for the presidency, a poll showed today.

The poll by BVA of voting intentions confirmed a slide in ratings for the 62-year-old former prime minister who, until the allegations about his wife broke on Jan. 25, had been seen as the frontrunner.

The poll gave Fillon between 18 and 20 percent of the vote in the April 23 first round, behind far-right leader Marine Le Pen on 25 percent and independent centrist Emmanuel Macron on 21-22 percent.

Le Pen, who heads the anti-immigrant and anti-euro National Front, would lose to Macron in the May 7 knockout by 34 percent to his 66 per cent, the poll found.

If Fillon did get through to the runoff against Le Pen she would lose, with 40 per cent of the vote to his 60 per cent.

A poll by Ifop Fiducial last night showed a similar slide in support for Fillon since the scandal emerged, though he has vowed to fight what he called a "demolition exercise".