Musk, whose AI startup xAI develops Grok, took to X - formerly Twitter - to blast Apple’s ranking policies.

He wrote: “Apple is behaving in a manner that makes it impossible for any AI company besides OpenAI to reach #1 in the App Store, which is an unequivocal antitrust violation.

“xAI will take immediate legal action.”

Musk also questioned why neither X nor Grok appeared in the App Store’s “Must Have” section despite claiming Grok ranks fifth “among all apps” and X being “the #1 news app in the world”.

The feud erupted amid renewed scrutiny of Apple’s App Store practices.

A U.S. judge recently referred Apple to federal prosecutors for criminal contempt over violations of an earlier injunction, while EU regulators fined Apple €500 million for hampering fair competition, citing its refusal to allow link-outs to external payment options.

OpenAI CEO Sam Altman quickly retorted to Musk’s comments, suggesting his complaints ring hollow given the Tesla owner’s alleged manipulations on X.

Altman said: “This is a remarkable claim given what I have heard alleged that Elon does to manipulate X to benefit himself and his own companies.”

As Apple faces mounting legal and regulatory challenges over its App Store practices, Musk’s threat adds fuel to the fire.

Whether the legal action materialises remains to be seen, but the spotlight on App Store fairness is sure to intensify.