Barnier, 73, the oldest premier in the history of modern France, has been tasked with forming "a unifying government in the service of the country", it said.

In a striking contrast, the former foreign minister succeeds Gabriel Attal, 35, a man less than half his age and who served only eight months in office.

The appointment of the veteran politician, a member of the right-wing Republicans (LR) party and not affiliated to Macron's centrist faction, was greeted with dismay by the left which may seek to topple him with a no-confidence motion.

A left-wing coalition emerged as France's biggest political force after the elections earlier this summer but with not enough seats for an overall majority.

Macron's centrist faction and the far right make up the two other major groups in the National Assembly.

Conservative ex-minister Xavier Bertrand and former Socialist prime minister Bernard Cazeneuve had been seen as the initial favourites to become premier, but both figures fell by the wayside with the mathematics of France's new parliament stacked against them.

In France, the president names the prime minster, who can then be censured by the lower house in a no confidence motion.

- Marine Le Pen 'decides' -

But Barnier, a right-winger and the European Union's former negotiator on Brexit, was Thursday lunch time seen emerging from talks at the Elysee with Macron to make a dramatic return to frontline politics as premier.

He has been all but invisible in French political life since failing to win his party's nomination to challenge Macron for the presidency in 2022 during a campaign where he tacked further right and suggested a moratorium on immigration.

The veteran former foreign minister and EU commissioner is "Macron-compatible" and would not be immediately voted out by parliament, an advisor to the president told AFP, asking not to be named.

A minister in the outgoing government, who also asked not to be named, said he was "very popular with right-wing members of parliament without being an irritant on the left".

Macron appears to be counting on the far-right National Rally (RN) of three-time presidential candidate Marine Le Pen not to topple Barnier if a no confidence motion is tabled.

"We will wait to see Mr Barnier's policy speech" to parliament, said Le Pen, the leader in parliament of the RN, the party with the most seats in the lower house following the snap polls.

RN party leader Jordan Bardella said Barnier would be judged "on evidence" when he addressed parliament.

The composition of the new cabinet will be closely watched for signs of concessions to Macron's political foes.

Greens leader Marine Tondelier earlier commented: "We know in the end who decides. Her name is Marine Le Pen. She is the one to whom Macron has decided to submit."

 'Tough' task

Hard-left leader Jean-Luc Melenchon, whose Unbowed party (LFI) and allies belong to a left-wing bloc, said Macron naming Barnier meant the election had been "stolen from the French".

Macron's decision comes under the gun of a deadline to submit a draft 2025 budget for France's strained government finances before October 1.

It also marks his attempt to acknowledge rejection of his seven-year rule without giving up on hard-fought reforms, chief among them last year's widely resented increase to the official retirement age to 64 from 62.

Barnier's "task looks tough, but difficulty has never scared him," said former prime minister Edouard Philippe who earlier this week announced he would seek to succeed Macron in 2027 presidential elections.

After the July election deprived Macron of his relative majority in parliament, the centrist president drew out the appointment of a new prime minister for a period unprecedented since World War II, through the July-August Olympic Games and beyond.

Speaking to Le Figaro daily and using rugby parlance, Attal expressed hope his successor could "convert the try" of the policies whose implementation he could not complete during his time in office.