Elon Musk has escalated his feud with the British caver involved in July’s rescue of a group of young Thai footballers, whom he had previously accused of being a paedophile.
Vernon Unsworth, 63, angered the technology billionaire when he derided his offer of sending a mini submarine to assist the rescue, pointing out that it was not a workable solution.
Last week he reignited the controversy by mocking Mr Unsworth for not following up on his threat to take legal action.
It later emerged that Mr Unsworth’s lawyers had in fact sent Mr Musk a letter on August 6, informing him of their intention to sue for the “false and defamatory statements.”
On Tuesday, Buzzfeed published emails Mr Musk sent last week, in which he launched another baseless attack on Mr Unsworth and called the journalist who has covered the dispute a "f-----g a--hole".
"I suggest that you call people you know in Thailand, find out what's actually going on and stop defending child rapists, you f----ing a--hole," Mr Musk wrote.
Mr Musk has offered no evidence to support his claims.
“As for this alleged threat of a lawsuit, which magically appeared when I raised the issue (nothing was sent or raised beforehand), I f---ing hope he sues me,” he added in the email.
Mr Unsworth's lawyer, L. Lin Wood, denied the latest accusation.
"Elon Musk can tweet his vindictive and vicious lie about Mr. Unsworth a hundred times and it will still be a lie," Wood wrote in a statement to Buzzfeed.
"After deleting the initial accusation and tweeting an apology, Mr Musk has continued to republish his false and unsupportable accusation. His conduct demonstrates that his recklessness is intentional and designed to harm Mr. Unsworth."
A Tesla representative has yet to respond to The Telegraph’s request for comment.