A British diver who helped in the rescue of the trapped boys from a Thai cave is to sue Elon Musk for branding him a child rapist.

Vernon Unsworth said he was preparing to start legal action against the Tesla billionaire imminently, the Daily Mail reports.

The 63-year-old is considering using Thai courts because they could hand Musk a jail sentence. He is also mulling defamation proceedings in London and the US where the tycoon is based.

The diver from St Albans in Hertfordshire described Musk's allegations that he had a child bride and had moved to an area notorious for child sex trafficking as '100 per cent untrue'.

"I've been told to be very careful because this guy may do anything to make my life difficult," he said.

Musk had accused Unsworth of being 'a paedo' during the rescue of 12 schoolboys from the Tham Luang Nang Non cave complex.

Earlier this week he renewed his baseless attack by telling a reporter to stop defending "child rapists" and claimed Unsworth had moved to Thailand for a "child bride who was about 12 years old at the time".

Unsworth's girlfriend, Woranan Ratrawiphukkun, 40, yesterday said she was "no child bride". She met him seven years ago, when she would have been at least 32.

She runs a nail salon and lives with Unsworth in the countryside at Chiang Rai – near the scene of the cave rescue.

She told the Times: "The news about him being married to a 12-year-old child is laughable. As of now, everything will proceed according to the law. Vern is a kind person. He rarely has an argument with anyone, and everybody loves Vern. If he wasn't a good man, we wouldn't still be together."

Unsworth was the first foreign rescuer on the scene of the cave drama. He had an intimate knowledge of the tunnel system in which the 12 schoolboys and their coach were trapped.

But he incurred Musk's wrath when he said a mini-submarine proposed by the tycoon to help in the rescue had 'absolutely no chance of working', describing the offer as a publicity stunt.

Musk provided no evidence for his initial jibe and later deleted the posts and apologised.

However, he has continued the attack in astonishing emails to a BuzzFeed reporter.

In the emails, which Musk, 47, claimed were off the record he said Unsworth was "an old, single white guy from England who's been travelling to or living in Thailand for 30 to 40 years, mostly Pattaya Beach, until moving to Chiang Rai for a child bride who was about 12 years old at the time."

He suggested Pattaya and Chiang Rai were hotspots of the child sex industry and added: "I f***ing hope he sues me."

Unsworth said he had never visited Pattaya or any other areas of Thailand with similar reputations for depravity.

"What Mr Musk is saying is any foreigner living in Thailand is a paedo guy," he added. "I've never been to places like Phuket, I've never been to Pattaya, I've never been to any of the islands."

Unsworth, a financial broker, splits his time between the UK and Thailand. He is being represented by US-based defamation lawyer Lucian Wood.

"Musk can tweet his vindictive and vicious lie a hundred times and it will still be a lie," said Wood. "Paedophilia is too serious an issue to leave unchallenged."