The latest comments from conservative Francois Fillon, who has accused the Socialist government of failing to protect candidates, underline the increasingly ugly tone of France's campaign.

A poll by Odoxa/Dentsu-Consulting showed Mr Macron, 39, a former economy minister running without the support of any traditional political party, would beat Ms Le Pen in the run-off with 61 per cent of the vote, versus 39 per cent for her.

Two new polls published on Sunday showed Le Pen still winning the first round of the election on April 23 with 27 percent, but with Macron closing the gap on her with 25 percent. Gael Nofri, a former aide of Le Pen, has claimed that he was recruited by National Front in 2012 for Le Pen's presidential campaign team on a fictitious contract under the European Parliament funding.

Macron has been lifted in polls by the alliance with centrist Francois Bayrou, leader of the MoDem party.

Despite all this, French voters who do not want Le Pen, who is now expected to make it into the second round of voting, are calm. Why?

"French people can't put up with mass immigration any more!" she said, again to cheers from the crowd waving French flags.

French presidential elections are still two months away, but revelations and allegations are coming out as though it were October 28 2016 all over again.

Sebastien Chenu of Le Pen's National Front party said on BFM television that the protesters were "trying to stop us from delivering our message".

He also mentioned Socialist candidate Benoit Hamon's choices on nuclear power as well as environmental and constitutional issues.

Some 2,200 demonstrators are estimated to have gathered in central Nantes to protest against Le Pen who is coming for a campaign rally ahead of this spring's presidential election.

"Mr. Macron went to Germany recently to express the admiration he had for their decision to welcome 1.5 million migrants", she said, referring to Chancellor Angela Merkel's policy of accepting refugees past year.

Despite the charges, Le Pen is leading the surveys regarding presidential elections.

French prosecutors extended the probe of Fillon, saying further investigation is needed and pushing any conclusion until after the election. "You have to ask why everything is accelerating and madame has been summoned two months before a major election date".