A British diver who helped rescue young football players trapped in a Thai cave is suing the Tesla chief executive, Elon Musk, for defamation.

Vernon Unsworth alleges that Musk falsely accused him on Twitter of being a paedophile. A lawsuit filed in Los Angeles federal court seeks at least $75,000 (£57,000) in damages and a court order preventing Musk from making further allegations, while Unsworth is also bringing action in the English and Welsh courts.

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Musk called Unsworth, who was instrumental in the successful rescue operation, a “pedo” after the diver criticised him in a television interview. Musk and SpaceX engineers built a small submarine and shipped it to Thailand to help with the cave rescue. The device was not used and Unsworth called it a PR stunt.

The diver alleges in his complaint that Musk later accused him of moving to Thailand to be with a bride who was about 12 years old. Unsworth says Musk “embarked on a PR campaign to destroy” his reputation after becoming angry at an interview he gave to the US television network, CNN.

Unsworth had told the broadcaster that Musk’s device “had absolutely no chance of working”, that Musk “had no conception of what the cave passage was like” and that Musk could “stick his submarine where it hurts”.

The diver accuses Musk of “publishing false and heinous accusations of criminality against him to the public”. In the court filing, seen by the Guardian, he adds that Musk posted a series of tweets directed at Unsworth on 15 July, calling his claims about the submarine into question and adding: “Sorry pedo guy, you really did ask for it.”

The complaint notes that Musk deleted the tweets and posted two more that “purported to be an apology” three days later.

Lawyers for Unsworth wrote to Musk threatening to sue on 6 August, though Musk publicly claimed about two weeks later that no such action had been taken. “You don’t think it’s strange he hasn’t sued me? “ he tweeted in response to another user.

The complaint says: “Musk’s 28 August tweet conveyed to the average reader that Mr Unsworth’s failure to sue him was evidence that Mr Unsworth is, in fact, a pedophile and guilty of the most heinous crimes.” That accusation was followed by a host of further similar allegations in an email from Musk to a reporter at Buzzfeed, which Unsworth’s lawyers argue are also untrue.

“Instead of retracting his false accusations and ceasing his campaign to impugn Mr Unsworth, Musk publicly stated, ‘I fucking hope he sues me,’” the US complaint says.

On Monday, Unsworth’s lawyer in the US, Lin Wood said: “Musk’s influence and wealth cannot … protect him from accountability for his wrongdoing in a court of law.”

Mark Stephens, of Howard Kennedy, who represents Unsworth in his action in the high court, said: “[Musk’s statements] show that [assertions] by the rich and powerful can circulate round the globe to their 22.5m followers and to the media before the truth can pull its boots on.

“Elon Musk is being brought to account for repeatedly attacking and taunting the good name of an ordinary spelunker, Vernon Unsworth, who answered the call and, with others, put his life on the line to help rescue the 13 trapped in the caves in Thailand. I still carry the light of hope that Mr Musk will withdraw his baseless allegations and properly vindicate Mr Unsworth.”