A US judge has dismissed a lawsuit by Elon Musk's X accusing a group of advertisers and major companies of illegally boycotting his platform.

Its parent company X Corp alleged in 2024 that firms including food giants Unilever and Mars, renewable energy firm Orsted and the World Federation of Advertisers (WFA) had conspired to deprive it of "billions of dollars" in advertising revenue.

But in Thursday's ruling, US District Judge Jane Boyle said the company had failed to show it had suffered any harm under federal competition laws.

The BBC has approached X for comment.

X Corp's lawsuit, filed in a Texas court in 2024, followed a decline in advertising revenue after Musk's acquisition of Twitter in 2022.

The tech billionaire had ushered in sweeping changes to the platform after purchasing it, including reinstating the accounts of controversial figures and lifting some content restrictions.

Within a year of Musk acquiring X, advertising revenue had fallen by more than half as some firms paused or reduced their promotions on the site.

The lawsuit claimed the group of advertisers had acted against their own economic self-interest to conspire against the platform, saying this violated US antitrust laws designed to promote fair competition between companies.

At the time, Musk tweeted: "We tried being nice for 2 years and got nothing but empty words. Now, it is war."

X Corp's lawsuit alleged that the accused firms had unfairly withheld spending by following safety standards set out by a WFA initiative called the Global Alliance for Responsible Media (GARM).

Garm's stated aim is to "help the industry address the challenge of illegal or harmful content on digital media platforms and its monetisation via advertising".

CVS and the other defendants denied any wrongdoing and, in counter-filings, urged Judge Boyle to dismiss the lawsuit.

They argued they had acted independently when making business decisions about when and where to spend advertising money, and said X had failed to illustrate otherwise.

Boyle appeared to agree, writing in an opinion filed alongside her judgment that Garm "did not buy advertising space from X to sell to advertisers nor did it, in such an arrangement, tell X not to sell directly to Garm's customers".

"The very nature of the alleged conspiracy does not state an antitrust claim, and the court, therefore, has no qualm dismissing with prejudice," she concluded.