The top candidates in France's presidential election have clashed in a televised debate, with centrist Emmanuel Macron accusing far-right leader Marine Le Pen of lying and seeking to divide the French.

The election is shaping up as the most unpredictable in decades, with Macron and National Front leader Le Pen tied in polls for the April 23 first round, while the mainstream left and right languish in third and fourth place.

One of the most heated exchanges in Monday's debate came between the two frontrunners after Le Pen accused Macron of being in favour of the burkini, a full-body swimsuit worn by Muslim women that created weeks of controversy in France last summer.

"You are making [French Muslims] enemies of the republic."



French presidential front-runners Macron and Le Pen clash in heated debate. pic.twitter.com/Ti03nx4gKc — Al Jazeera English (@AJEnglish) March 21, 2017





"You are lying [to voters] by twisting the truth," retorted Macron, a former economy minister who is running as an independent.

"The burkini is a public order problem. Do not use it to divide the French," he said, accusing Le Pen of transforming "the over four million French people, whose religion is Islam ... into enemies of the Republic".

OPINION: All about security in France's elections

"I want to put an end to immigration, that's clear," Le Pen said, before talking about a rise of "Islamist fundamentalism" in France and saying the security situation was "explosive".

ANALYSIS BY AL JAZEERA'S NATASHA BUTLER, PARIS Marine Le Pen has given quite a strong performance, sticking to her regular themes of anti-immigration, anti-globalisation, about needing to restore sovereignty. You can see she's a veteran politician. She's self-assured, she knows how to try and convince voters.

Emmanuel Macron really went into this debate very much untested. He's got very little political experience. He's a former banker and a former finance minister but he's never been elected. He really needed to show that he has what it takes to be the next president. So far, he's given quite a weak performance. His confidence has picked up a bit but he looked extremely nervous at the beginning.

One thing that's been interesting to watch is Francois Fillon. He really needed to do well in this debate, trying to revive this campaign after weeks of legal woes and allegations. So far, he's really done that. He's looked very serene, very calm, he's really stayed above the fray when the others have gotten into arguments. So this could be a bit of a win for Fillon.

The Socialist Party's Benoit Hamon took issue with Le Pen's claim that public schools are wracked by violence, calling her remarks "nauseating".

The debate, the first between the five main contenders before a two-round election on April 23 and May 7, could help viewers make up their minds in an election where nearly 40 percent of voters say they are not sure who to back.

While polls show Macron and Le Pen establishing a clear lead in the first round, conservative candidate Francois Fillon, the one-time frontrunner, has fallen back, damaged by a scandal surrounding the employment of his wife as a parliamentary assistant.

Fillon, accused of paying his wife a generous salary for work she may not have done, has been put under formal investigation, a first for a French presidential candidate.

Only the top two candidates go through to the runoff, where polls show Macron easily beating Le Pen.

But with so many voters undecided and polls showing the abstention rate could be higher than ever in France, the level of uncertainty remains high. A high abstention rate could benefit Le Pen as polls consistently show that her supporters are the most certain of their vote.

The election is taking place against a backdrop of high unemployment and sluggish growth.

Fillon said Le Pen's proposal to ditch the euro and bring back the French franc would cause "economic and social chaos".

"You don't leave the euro and the protection afforded by the European Central Bank ... for an adventure ... that would ruin borrowers and savers alike," Fillon said.

Le Pen, who has been buoyed by Donald Trump's election in the US and Britain's decision to leave the EU, accused Fillon of scaremongering.

"That's called Project Fear, Mr Fillon. It was used before Brexit," said Le Pen, who has pledged a similar referendum on France's EU membership.

A total of 11 candidates are running for president. Six smaller candidates were excluded from Monday's debate.