In a bizarre video posted to X, the company’s CEO Linda Yaccarino said the legal action was a response to evidence recently heard by a Republican-led committee of the US House of Representatives.

The antitrust lawsuit has been filed in a federal court in Texas against the World Federation of Advertisers (WFA) and member companies Unilever, Mars, CVS Health and Orsted.

It focuses in particular on the Global Alliance for Responsible Media (GARM), a WFA initiative established in 2019 to “help the industry address the challenge of illegal or harmful content on digital media platforms and its monetisation via advertising”.

GARM was set up in the wake of the Christchurch Mosque shootings in which the killer livestreamed the attack on Facebook. This followed a slew of high-profile cases where brands’ advertisements appeared next to illegal or harmful content, such as child pornography and content promoting terrorism.

X, previously a member of GARM, announced at the start of July that it was rejoining GARM.

Ms Yaccarino said: “These organisations targeted our company… The evidence and facts are on our side. They conspired to boycott X, which threatens our ability to thrive in the future.”

She added: “People are hurt when the marketplace of ideas is constricted. No small group of people should be able to monopolise what gets monetised.”