Le Pen denies 'secret agenda' to exit EU

"I think a large majority of French people no longer want the European Union as it exists today, which is a European Union that functions in an absolutely undemocratic way, which advances by threat, by blackmail and which implements policies that are against the interests of the people."

Le Pen has ditched past plans to haul France out of the EU, its free-movement Schengen zone and the euro.

However, she remains deeply euro-sceptic. She says she would renegotiate the agreement on Schengen and increase the number of customs agents, reintroducing checks on goods entering the country from other EU states.

Also on Tuesday, Le Pen said Macron's offer to soften planned pension reforms is a "manoeuvre" to lure voters ahead of the April 24 vote.

"It's a manoeuvre by Emmanuel Macron to try to win over, or at least to mitigate the opposition of the left-leaning voters", she said.

Campaigning in France's former industrial heartland, Macron on Monday said he was prepared to readjust his planned pension reform, which is at the core of his program for re-election.

"I am ready to change the timeline and say we don't necessarily have to do a reform by 2030 if I feel that people are too anxious", Macron said.

He was also prepared, he said, to "open the door" on pushing the country's retirement age from 62 at the moment to 64, rather than 65, his initial proposal.

Manuel Bompard, the head of the campaign of far-left candidate Jean-Luc Melenchon, who came in third in the first round, said he did not agree with Macron's or Le Pen's retirement proposals.

An Ipsos-Sopra Steria poll cited by Public Senat said 23 per cent of Melenchon voters would now support Macron, 15 per cent Le Pen and a further 62 per cent did not take a position.

Macron and Le Pen traded blows on Monday as they sought to appeal to left-leaning voters who now face the tough decision whether to give their vote to a far-right populist or to a liberal many opponents branded a "president of the rich".