The race appears to be narrowing down to the two finalists of the 2017 election, and while Macron so far has kept clear of any direct debate, the two have increasingly taken aim at each other from afar. And they were not mincing their words on Friday.

"There was a clear strategy (from Le Pen's camp) to hide what is brutal in her programme," Macron told Le Parisien in an interview published on Friday.

"Her fundamentals have not changed: It's a racist programme that aims to divide society and is very brutal."

Le Pen told broadcaster Franceinfo that she was "shocked" at the accusation, which she rejected, branding the president "febrile" and "aggressive".

She said her programme, which includes adding a "national priority" principle to the French constitution, would not discriminate against people on grounds of their origin - as long as they held a French passport.

Macron is ahead in opinion polls, which still see him as the most likely winner, but his re-election is no longer a foregone conclusion. Le Pen's solid comeback in opinion polls has put her victory within the margin of error in some surveys.

A poll on Thursday showed the tightest ever gap in support between the two rivals, with Marine Le Pen seen winning 49 per cent of votes in a likely runoff against the president, her best polling score on record.

Le Pen has centred her bid on purchasing power, softening her image and tapping into the voters' main concern by promising to cut taxes and hike some social benefits, worrying financial markets as she gains momentum in the polls.

Rival far-right candidate Eric Zemmour's radical, outspoken views have helped her look more mainstream and many left-leaning voters have told pollsters that, unlike in 2017, they would not vote in the second round to keep Le Pen out of power.

"They won't necessarily vote for Marine Le Pen, but they don't want to vote for Emmanuel Macron," said Jean-David Levy, the deputy director of polling institute Harris Interactive.

"Marine Le Pen has never been so capable of winning a presidential election"

According to opinion polls, around a third of voters still haven't made up their minds, which analysts say often favours candidates with realistic chances to enter the second round as undecided voters tend to go for what French call a "useful vote", meaning voting strategically.

Other than Macron and Le Pen, this trend is set to favour far-left veteran Jean-Luc Melenchon who - also on an upward trend - ranks third with around 17 per cent of forecast votes.

On Thursday, left-wing figure Christiane Taubira, a former minister who dropped out of the race after she failed in her attempt to rally the left behind her, endorsed Melenchon, saying he was now the left's best hope.

Macron expressed regret on Friday for having entered the race late, saying he had had no choice because of the war in Ukraine.

On his last day left ahead of the first vote, Macron chose to focus on younger voters campaigning around Paris and an evening interview with a social media news outlet.

Australian Associated Press