Marine Le Pen accused her main rivals in France's presidential race of promoting "project fear" over her plans to leave the European Union and the euro in an unprecedented televised debate on Monday night.

Brexit was the focal point of one of the most violent clashes in the three-hour debate - the first of three before the first round of voting on April 23 - in which the five main candidates finally started discussing policy in a campaign dogged by sleaze allegations.

In one of a series of heated exchanges, conservative nominee François Fillon accused Ms Le Pen of being a "serial killer" of the French economy in her plan to exit the euro, restore the franc, and to hold a referendum on leaving the EU.

"You are dragging the country towards veritable economic and social chaos, which would lead to the ruin of both borrowers and savers," he said.

Polls suggest that almost three quarters of the French are against Ms Le Pen’s plan to replace the euro with the franc, with many fearing it could spark a bank run if she was elected.