Paris (AFP) - French presidential frontrunner Emmanuel Macron attacked far-right leader Marine Le Pen over her economic policy and plans to scrap the euro on Tuesday in an unprecedented debate between all 11 contenders ahead of this month's election.

The discussion was at times chaotic and dominated by the anti-capitalist and virulently anti-EU smaller candidates who made their first major appearance ahead of the first round of the two-stage vote on April 23.

The most telling clash between the frontrunners came at the end of the first section when 39-year-old Macron took on what is considered one of Le Pen's vulnerabilities -- her plans to scrap the euro and revert to the franc.

"What you are proposing, Madame Le Pen, is a reduction in French people's spending power because, by withdrawing from the euro, for savers, workers, it's a reduction in spending power," he said.

Polls show only a third of French voters support scrapping the euro, many of them anxious about the impact of a devaluation which would hit their savings and spur inflation.

The clash and Macron's more combative performance could point to the tone and shape of the campaign ahead, with Macron and Le Pen having emerged as the clear frontrunners.

Macron accused her of wanting to start an "economic war" with France's neighbours and denounced her nationalist stance, which he said had torn the continent apart in the past and filled graveyards near his hometown Amiens in northeast France.

With just 19 days until the first round of voting in a rollercoaster contest, the debate could influence the momentum of the campaign, with around a third of voters still unsure of how they will vote.

Polls show far-right candidate Le Pen and centrist independent Macron in a dead heat at around 25 percent heading into the first round on April 23. Macron is seen easily winning the second round on May 7.

- 'Unfettered globalisation' -

Le Pen put in a steady performance under fire, warning about the closure of factories, and the danger of Islamists and immigrants eroding France's national identity.

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"I consider that in this election our civilisation is at stake," she said at the start of the debate, promising to restore order and combat "unfettered globalisation".

When questioned about legal problems surrounding her National Front party including campaign financing and the use of expenses at the European parliament, she said she considered herself to be "politically persecuted".

Socialist candidate Benoit Hamon scoffed at her defence, saying it was "amusing to see you playing the victim while spending your time attacking immigrants".

For the second time, Hamon found himself eclipsed by his rising far-left rival Jean-Luc Melenchon, who put in another assured performance, according to a poll published by BFM television after the debate.

One candidate who needed to shine was conservative Francois Fillon, whose campaign was almost derailed by criminal charges over claims he paid his wife hundreds of thousands of euros for fake parliamentary jobs.

He concluded by saying that if voters did not want the "the chaos proposed" by Le Pen or "the continuity" represented by Macron, then they should vote for him.

Unlike the first debate, Tuesday's featured all of the candidates ahead for the first time in French history.

They included fast-talking autoworker Philippe Poutou, who featured widely on social media after taking on Le Pen and Fillon over their legal problems in unusually blunt language.

"With Fillon, the more you look the more corruption and cheating you find," he said.

Communist firebrand Nathalie Arthaud vowed to protect French workers from being "strangled by the capitalist system", while anti-EU nationalists such as Francois Asselineau, Nicolas Dupont-Aignan and Jacques Cheminade enjoyed rare airtime.

- 'Race to the bottom'? -

It was the first time that all candidates had debated before the first round of a presidential election in France with many observers sceptical about whether the format would help inform voters.

Writing in Le Monde before the debate, Michel Noblecourt, noted that President Francois Hollande -- who decided in December not to seek re-election -- warned that the "dangerous" innovation in French politics risked "a race to the bottom".

The final result of an election that is being watched closely around the world is still seen as highly unpredictable.

Dissatisfaction and outright hostility towards mainstream politics is high in France and surveys show around a third of voters plan to abstain.