Voting intentions for centrist French presidential candidate Emmanuel Macron have slipped below 60 percent for the first time since 17 March ahead of the 7 May run-off, according to the daily Presitrack poll produced by pollsters Opinionway.

Presitrack said in its survey on Thursday that 59 percent of votes would be cast for the long-time favourite Macron versus 41 for Marine Le Pen, compared with 60 percent and 40 percent respectively reported in its poll a day earlier.

The rolling three day poll of 1,800 people included intentions collected on Wednesday, a day when Macron and Le Pen clashed over the future of the Whirlpool tumble drier factory in Macron's home town of Amiens.

Ahead of the first round that put Macron and Le Pen through to the run-off, Presitrack had Macron on 64-65 percent of the vote.