European Commissioner Thierry Breton, who pursued Elon Musk over content regulation on social media site platform X, has resigned from his role, accusing European Commission President Ursula von der Leyen of acting against him.

Breton was the European commissioner for the internal market for five years from December 2019, in a role that gave him oversight of the smooth and fair running of the European single market, both physical and digital.

In the latter part of this term, he had been at the forefront of enacting Europe’s Digital Services Act (DSA), which was introduced in 2022 with the aim of creating a level playing field in Europe’s digital market in the face of big tech giants, as well as to moderate illegal content and disinformation.

Von der Leyen is in the process of appointing a new European Commission, having been renewed in her role for a second term in July, following European Parliamentary elections in June, in which her European People’s Party won the most seats.

The commission is made up of members from each of the 27 EU member states. French President Emmanuel Macron had renewed Breton as France’s representative on the commission. He had been tipped for another important portfolio as well as potentially the executive vice presidency.

In his resignation letter, posted on X, Breton openly accused von der Leyen of politicking against him.

“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.

Breton and von der Leyen have been odds ever since the former publicly voiced disquiet about the latter’s parliamentary election campaign as well as her being reappointed as European Commission President for a second term.

He also found himself at odds with von der Leyen in August when he sent a letter to Musk, urging him to ensure that X adhered to EU regulations and moderated content, ahead of the tech tycoon’s live interview with U.S. presidential candidate Donald Trump.

In response, Musk told Breton to back-off with an expletive-laden meme on X, taken from the satirical action thriller Tropic Thunder.

The European Commission would not comment on the insult, but a spokesperson stated that “the timing and wording” of Breton’s letter to Musk had not been coordinated with von der Leyen or other commissioners, in a response that was seen as a rebuke to the commissioner.

The European Commission announced last December that it had opened formal proceedings to assess whether X may have breached the DSA “in areas linked to risk management, content moderation, dark patterns, advertising transparency and data access for researchers”.

In a first finding, the commission announced in July that its investigation suggested that X’s blue user checkmarks had breached the DSA, by giving false credibility to some accounts. Other aspects of the investigation are ongoing.