France’s already enfeebled centre-right party is in turmoil after one of its leaders struck a deal with the rival party of President Emmanuel Macron for next month’s regional elections, underlining the current dominance of national politics by Macron and the far-right leader Marine Le Pen.

Renaud Muselier, the elected Les Républicains (LR) president of the Provence-Alpes-Côte d’Azur region, was stripped of the party ticket after the announcement of an electoral pact with Macron’s La République en Marche party designed to ward off the threat of a victory by Le Pen’s Rassemblement National.

Although the pact involved Macron’s LREM party withdrawing its separate challenge for the region and backing Muselier as a candidate, LR leaders were furious about what some termed a betrayal or a “takeover” and said it would be counterproductive in the struggle to keep the extreme right from power.

“Immense sadness about this stab in the back,” said LR parliamentarian Eric Ciotti, adding that he knew “they were preparing their vile soup in the Elysée kitchen”.

LR leader Christian Jacob immediately announced that the incumbent Muselier would not be an LR candidate. “Fear of losing on one side and cynicism on the other have never produced a political programme,” he said in a statement.

Unlike Macron’s centrist party, created only five years ago before his successful bid for the presidency in 2017, the Gaullist LR has a long pedigree and is strong at the local and regional levels of French politics, and therefore also in the Senate.

But at the national level, the party has struggled since Macron’s victory in the presidential and legislative elections. In the European elections in 2019, the LR received less than 8.5 per cent of the votes in France, behind even the greens.

Along with the dizzying decline of the Socialists and the Communists on the traditional left, that has left Macron and Le Pen as the dominant players on the national stage, and the latest opinion polls show them to be the two candidates likely to qualify for the run-off in the presidential vote a year from now. Both are attempting to appeal to voters on the right by emphasising their dedication to law and order and determination to crack down on Islamists.

Thierry Mariani, a defector from the LR who is now Le Pen’s RN candidate in the south-east for the regional elections at the end of June, lost no time in mocking his old party for compromising itself. “Little by little, the party is losing its way,” he told BFMTV.

Muselier’s controversial electoral pact with Macron’s party, announced by Prime Minister Jean Castex at the weekend, is unusual because it precedes the first round of the election. Normally, politicians take such steps only after the initial voting, with left and right frequently making deals in what is known as a “republican front” to keep out Le Pen and the far right.

“Macron wants to prove, a year before the presidential election, that an alliance between him and the right is unavoidable,” the rightwing newspaper Le Figaro said in a front-page editorial on Monday.

“It’s a risky bet. On the evening of June 27 [when regional election results are announced] if his pioneer candidate loses, the LR-LREM alliance, presented as a rampart against the RN, will seem more like a stepping stone.”