The top candidates in France's presidential election clashed in a TV debate with Emmanuel Macron accusing far-right leader Marine Le Pen of lying and 'twisting the truth' over claims he supports the burkini.

The debate, the first between the five main contenders ahead of a two-round election on April 23 and May 7, could help viewers make up their minds in the election where nearly 40 per cent of voters are still unsure who to vote for.

Opinion polls show Macron and Le Pen pulling away from the pack in an election that has been full of twists and turns, and which is taking place against a backdrop of high unemployment, sluggish growth, a continuing terrorist threat and rows about immigration, integration and racism.

Francois Fillon, Emanuel Macron, Jean-Luc Melenchon, Marine Le Pen and Benoit Hamon before the debate

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

He reacted vigorously when Le Pen essentially suggested that her rival isn't really committed to France's secular values and policies.

'I don't need a ventriloquist,' he retorted. 'When I have something to say, I say it clearly.'

Macron, 39, who is running as an independent, retorted: 'You are lying (to voters) by twisting the truth.'

Also in the debate, while setting out her vision of a France which defends its interests 'without being lectured by a supranational body', Le Pen, who has accused Germany of dictating to the rest of Europe, said: 'I have no desire to be Mrs Merkel's deputy'.

The exchange on TF1 television grew feisty when the candidates were asked about migration and Islam.

'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 in France was 'explosive'.

An attack at Orly airport in Paris on Saturday, when a man known to police as a radicalised Muslim was shot dead after trying to grab a soldier's rifle, has put security back in the spotlight after a series of Islamist attacks have rocked the country.

She also attacked Macron on his foreign policy calling it 'completely empty...we don't know what you want.'

Macron, in turn, rounded on Le Pen for using Islam to divide the French.

Le Pen wants all visible religious symbols worn by people, including Muslim headscarves and Jewish kippahs, banned from public.

He said: 'The trap you are falling into, Madame Le Pen, with your provocations is to divide society.'

Le Pen said France should oppose multiculturalism, but was accused by Macron of making enemies of Muslims in the country

After Britain's Brexit vote and the election of Donald Trump in the United States, markets are nervous about the possibility of a Le Pen victory.

She is pledging to take France out of the euro and wants to hold a referendum on EU membership.

She said she did not want to see France become a 'vague region' of the bloc.

'I don't want to be the vice chancellor of Angela Merkel,' she said, referring to the German leader.

Former frontrunner Fillon, 63, 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, who presented himself as the most experienced pair of hands, scolded.

Le Pen 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, said.

But Macron, staunchly pro-Europe, noted that 'all those who said Brexit will be wonderful…ran away and hid'.

Francois Fillon shakes hands with left-wing Benoit Hamon during the fiery TV debate tonight

Although Marine Le Pen (pictured) is currently France's most popular politician, she provokes strong emotions and in the second round many voters are expected to vote for 'anyone but Le Pen'

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

Only the top two candidates go through to the runoff, where polls show Macron edging out 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 her supporters are the most certain of their vote.

Fillon, accused of paying his wife [and two children] for work they may not have done, has been put under formal investigation, a first for a French presidential candidate.

He said: 'I may have made mistakes. I have defects. Who doesn't? But I have experience.'

But the scandal, which has dominated the campaign for weeks, occupied relatively little time in the debate, with only firebrand leftist Jean-Luc Melenchon going after Fillon and Le Pen, herself the target of several judicial probes.

Macron, a former investment banker who has never run for elected office, came under criticism for private donations made to his campaign.

Socialist candidate Benoit Hamon suggested he could fall under the influence of lobbies in the pharmaceutical, banking or oil industry.

But Macron claimed he was the only candidate who was not funded by public money, saying: 'I pledge to be controlled by no one.'

Macron made a name for himself by criticising sacred cows of the French 'social model' such as the 35-hour working week, iron-clad job protection and civil servants' jobs for life.

Francois Fillon (pictured, right, with his British wife Penelope) was the early favourite when he won the conservative primary last year but his popularity has plummeted after a series of scandals about payments made to members of his family

Opinionlab reports that the latest tracking poll has Le Pen on 27 per cent, with Macron on 23 percent and the scandal-hit Francois Fillon on 18 per cent.

The Socialist candidate Benoit Hamon is far behind on 13 percent, with far-Left candidate Jean-Luc Mélenchon on 12 percent.

Only two candidates go through to the second round - on May 7 - and at the moment Macron is seen beating Le Pen in the second round by 60 per cent to 40 per cent.

If Macron's campaign were to come unstuck and Fillon makes it through to the second round he would also beat Le Pen, by 55 percent to 45 percent.

Le Pen has to somehow find a way to appeal to moderate voters if she is not to face the same fate as her father Jean-Marie Le Pen, who made it through to the second round of the presidential elections in 2002 only to be thrashed by Jacques Chirac, who won 82 percent of the votes.

Last week another far-Right candidate, Geert Wilders, failed to make the breakthrough he was predicting in the general election in the Netherlands.

Afterwards the Dutch Prime Minister, Mark Rutte, said the 'wrong kind of populism' had been defeated.