A British rescue diver who was instrumental in the rescue of 12 children trapped in a Thailand cave is suing Tesla CEO Elon Musk for defamation.

Vernon Unsworth and his attorneys filed their lawsuit on Monday, arguing that the businessman had crossed a line by repeatedly insisting that Mr Unsworth is a paedophile and “child rapist”. Musk did not substantiate his claims against the diver.

They are seeking $75,000 over the claims made by Musk. Mr Unsworth has also filed lawsuits in English and Welsh courts.

Musk originally attacked Mr Unsworth in July, after the diver criticised a mini-submarine that Musk and his engineers built to rescue 12 boys in a Thai youth football team and their coach from a flooded cave system in Chiang Rai province. His first attack called Mr Unsworth a “pedo guy” on Twitter, suggesting that the diver is a paedophile.

The billionaire later publicly apologised, but then called him a paedophile once again in August when he asked on Twitter why he had not been sued if his allegations were untrue.

Musk then sent a series of emails to Buzzfeed News, alleging that Mr Unsworth is a “child rapist” who took a 12-year-old bride. He also claimed that Mr Unsworth had to be asked to leave the cave site during the rescue operations. None of those claims have been substantiated.

“Elon Musk falsely accused Vern Unsworth of being guilty of heinous crimes,” Mr Unsworth’s lawyer, L Lin Wood, said in a statement provided to the media. “Musk’s influence and wealth cannot convert his lies into truth or protect him from accountability for his wrongdoing in a court of law.”

Mr Unsworth’s lawyer in the UK, Mark Stephens, said the following in a statement: “Twibels (Twitter libels) show that falsehoods by the rich and powerful can circulate round the globe to their 22.5 million 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,” the statement continues. “I still carry the light of hope that Mr Musk will withdraw his baseless allegations and properly vindicate Mr Unsworth.”

A request for comment from Musk and Tesla was not immediately returned.

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The whole affair started in July, when the billionaire pledged that he would lead a team of engineers to build a mini-submarine that could make its way through the cramped cave caverns, and eventually bring the boys to safety.

Meanwhile, an international team of divers and rescue workers laboured to bring the boys to safety, and managed to do so on July 10. The mini-submarine was not used in the effort – and at one point Mr Unsworth told CNN that he thought Musk’s involvement was a “PR stunt”, that the submarine had “absolutely no chance of working”, and that Musk could “stick his submarine where it hurts”.

Musk responded two days later, tweeting that Mr Unworth was a paedophile. He said he would make a video of the mini-submarine working to prove his critic wrong.

“Sorry pedo guy, you really did ask for it,” he wrote.