An influential French member of the European Union’s powerful executive branch has resigned, calling into question the leadership of European Commission president Ursula von der Leyen just as she tries to assemble a new team for the next five years.

Thierry Breton, a French business executive and commissioner for the EU’s vast internal market who recently clashed with tech billionaire Elon Musk, suggested that Ms von der Leyen had gone behind his back to get another French official named in his place to the next commission.

In a post on social media platform X containing his resignation letter to the EU’s top official, Mr Breton said that Ms von der Leyen’s move was “further testimony to questionable governance – I have to conclude that I can no longer exercise my duties in the College”.

The commission proposes legislation for the 27 EU member countries and ensures that the rules governing the world’s biggest trading bloc are respected.

It is made up of a college of commissioners with a range of portfolios similar to those of government ministers, including agriculture, economic, competition, security and migration policy.

Mr Breton’s surprise resignation came just 24 hours before Ms von der Leyen was due to announce her new team to the European Parliament.

The commission was scheduled to start work on November 1, but speculation is rife that it might not get down to business before January.

European Commission spokeswoman Arianna Podesta said that Ms von der Leyen had accepted Mr Breton’s resignation and thanked him for his work during her first term.

Ms Podesta declined to comment on his very public criticism of the president’s leadership.

Within hours, President Emmanuel Macron nominated France’s foreign minister, Stephane Sejourne, in Mr Breton’s place.

The commission could not say who might take over Mr Breton’s responsibilities, which have included efforts to expand Europe’s defence industry to make more weapons and ammunition for Ukraine.

With an eye to keeping a gender balance within the commission for her second term at the helm, Ms von der Leyen had asked each member country to supply the name of a male and female candidate for policy commissioner.

Most only proposed one candidate, often a man.

The commission chief, a former German defence minister, has been pressuring smaller countries to change their minds.

In recent weeks, a man who was the preferred candidate of the government in Slovenia withdrew and a woman was proposed in his place.

Ms von der Leyen decides which country gets which portfolio, and some of them, such as those involving trade or finance or EU enlargement, are coveted by certain countries.

Plum jobs such as the post of “vice president” – the commission has seven of these – are also much sought after.

Mr Breton suggested that he was a victim of these political machinations.

“A few days ago, in the very final stretch of negotiations on the composition of the future College, you asked France to withdraw my name – for personal reasons that in no instance you have discussed directly with me – and offered, as a political trade-off, an allegedly more influential portfolio for France in the future College,” he wrote in his resignation letter.

“You will now be proposed a different candidate,” he said.

In any case, nothing is set in stone.

The commission nominees must still pass a grilling in the European Parliament to take office.

Mr Breton has irritated some in the commission with his go-it-alone approach.

Acting last month without Ms von der Leyen’s approval, he took to X to warn Mr Musk of possible “amplification of harmful content” by broadcasting an interview with former US president Donald Trump.

Mr Musk, who owns the social media platform, posted a derogatory reply.

Trump campaign spokesperson Steven Cheung urged the EU to “mind their own business instead of trying to meddle in the US presidential election”.