(AFP) - France headed into a new political crisis Tuesday as opposition lawmakers vowed to topple the minority government of Prime Minister Michel Barnier in a no-confidence vote after just three months in office.

A standoff over an austerity budget, which has caused jitters on financial markets, follows months of tension since President Emmanuel Macron appointed the 73-year-old in September.

The far-left France Unbowed (LFI) opposition party said it would bring a no-confidence motion after Barnier used executive powers Monday to force through social security legislation without a vote.

Marine Le Pen's far-right National Rally (RN), which has demanded changes to the 2025 budget, said it would back the LFI move.

French legislators were expected to vote on the motion Wednesday, with first results around 1900 GMT.

Two no-confidence motions will be put forward. One by the far right is unlikely to pass. Another proposed by the hard-left should go through with backing from RN lawmakers.

"Blocking this budget is, alas, the only way the constitution gives us to protect the French people from a dangerous, unfair and punitive budget," Le Pen said on X.

Barnier warned against the move.

France's situation is "very difficult in economic and social terms," Barnier told the National Assembly lower house. The vote would "make everything more difficult and more serious," he added.

- 'Didn't think she'd dare ' -

Macron, currently on a visit to Saudi Arabia, has appeared to be mostly a spectator in the crisis he unleashed by ordering snap elections in June, prompting some voices to question if he should consider resigning.

The turbulence has intensified political instability in the key EU member following the inconclusive elections called by Macron in a bid to halt the rise of the far right.

Barnier has been under pressure to cut 60 billion euros ($64 billion) off government spending in 2025 in a bid to cut the public-sector deficit to five percent of gross domestic product, from 6.1 percent of GDP this year.

He has made a number of concessions to the opposition including scrapping plans for a less generous prescription drug reimbursement policy from next year. But Le Pen has still opposed Barnier's plan.

Le Pen kept asking for concessions and Barnier had not thought she would back a no-confidence motion, a political source said.

"I didn't think she'd dare," Barnier said on Monday, according to the source.

Jockeying for leadership positions has started, with Socialist party boss Olivier Faure saying Macron must "appoint a left-wing prime minister".

But economists at ING said the likelihood of quickly finding a replacement for Barnier was "highly uncertain" because the National Assembly is so divided.

- 'President's responsibility' -

In a poll published on Monday, 52 percent of French people said they favoured Macron resigning, but were above all concerned about their purchasing power.

"I'm very worried and very upset with the forces on the left and the forces on the far right," Bertrand Chenu, a 65-year-old retiree, told AFP in Paris.

In Strasbourg, Emmanuel Parisot, 51, said the crisis was Macron's fault because he dissolved parliament and called snap polls.

"It's all the president's responsibility," Parisot said. "We don't know where that's going to lead."

If the government falls, it would be the first successful no-confidence vote since a defeat for Georges Pompidou's government in 1962, when Charles de Gaulle was president.

The lifespan of Barnier's government would also be the shortest of any administration of France's Fifth Republic which began in 1958.

Some observers have suggested that Le Pen, 56, is playing a high-risk game and seeking to bring down Macron before his term ends by ousting Barnier.

Le Pen is embroiled in a high-profile embezzlement trial. If found guilty in March, she could be blocked from participating in France's next presidential election, scheduled for 2027.

If Macron stepped down soon, an election would have to be called within a month, potentially ahead of the verdict in her trial.

"She could hope, if she won, to be in the Elysee Palace by early February," said Mujtaba Rahman, managing director for Europe at Eurasia Group.

© Agence France-Presse