Emmanuel Macron remains favourite to win France's turbulent presidential election race, a poll showed on Sunday, on the eve of a first televised debate which could allow embattled conservative Francois Fillon to get back in contention.

Macron, a former economy minister running as an independent centrist, would lead first-round voting with 26.5 percent, just ahead of far-right leader Marine Le Pen on 26 percent, before beating her 64-36 in the run-off, according to the Odoxa poll.

Fillon scored 19 percent of first-round voting intentions in the poll, confirming the task faced by the one-time frontrunner to revive a campaign sapped by a fraud investigation.

A separate poll by Kantar Sofres-Onepoint showed a similar trend for the first round, with Macron and Le Pen tied on 26 percent, ahead of Fillon on 17 percent.

French voters go the polls on April 23 and May 7 in the two-round election, which is being closely followed outside France as another test of popular discontent with traditional parties and institutions like the European Union.

The official campaign period got under way on Saturday when France's Constitutional Council announced a list of 11 contenders who had met conditions to stand.

The list also includes Benoit Hamon, candidate of the bitterly divided Socialist party of current president Francois Hollande, and left-wing firebrand Jean-Luc Melenchon who are running fourth and fifth, respectively, in opinion polls.

The Left's divisions have favoured the emergence of 39-year-old Macron, a former investment banker who resigned from Hollande's government last year.

"Politically, he is managing, so far, an incredible synthesis stretching from Sarkozy to Melenchon via Hollande," Odoxa said of Macron's support base.

Former President Nicolas Sarkozy was defeated by Fillon in a conservative primary last year.

Socialist Hamon, who scored only 12-12.5 percent in Sunday's polls, tried to rouse left-wing voters on Sunday with a rally at one of Paris' biggest concert venues, blaming Fillon and Macron for "a campaign polluted by money".

Like Fillon, Hamon will also be hoping to make up ground thanks to Monday evening's TV debate, which will bring together the five leading candidates.

Prospects for economic recovery, reducing the high level of unemployment, and immigration are themes likely to dominate Monday's debate.

A foiled attack at a Paris airport on Saturday, in which soldiers shot dead a man who shouted he wanted "to die for Allah" as he tried to seize a rifle, has also rekindled debate about security after two years of attacks in France by Islamist militants.

Both National Front leader Le Pen, running on an anti-immigration, anti-EU ticket, and Fillon criticised the Socialist government for failing to tackle security threats despite implementing state of emergency legislation in 2015 after 130 people were killed in shootings by Islamist militants in Paris.