France's powerful European commissioner Thierry Breton has announced he was quitting his role with immediate effect, claiming EU chief Ursula von der Leyen had sought at the last minute to bar him from her incoming team.

The shock resignation of the bloc's internal market commissioner comes on Monday, a day before von der Leyen was expected to unveil the makeup of her next commission, in the wake of EU-wide elections in June.

President Emmanuel Macron had put Breton's name forward for France's spot on the EU executive team, and his reappointment to a sizeable role — reflecting the country's weight within the 27-nation bloc — had been taken as a given.

"In the very final stretch of negotiations on the composition of the future College, you asked France to withdraw my name," Breton wrote in a scorching letter to von der Leyen, posted on X.

"In light of these latest developments — further testimony to questionable governance — I have to conclude that I can no longer exercise my duties in the College," he wrote.

"I am therefore resigning from my position as European Commissioner, effective immediately."

The European Commission did not immediately respond to a request for comment.