Elon Musk has become involved in a spat with the British rescue diver responsible for saving 12 Thai boys from a flooded cave - labeling him a 'pedo guy' in an astonishing and unsubstantiated personal attack.

The boys and their football coach were saved from the Tham Luang cave by an international team following a week of tense rescue missions.

In the face of backlash over his baseless comment, the billionaire doubled down, claiming the expat diver's decision to live in Thailand was suspect ('sus').

Vernon Unsworth (left) a British caver who lives in Thailand lashed out after Elon Musk (right) travelled to Thailand and to build 'a mini submarine'

Elon Musk designed a child-sized submarine out of rocket parts that he hoped could be used to rescue some of the soccer players trapped in a flooded cave in Thailand

Writing via his Twitter page, he attempted to cast doubt on whether the Brit was even involved in the rescue.

'Never saw him at the cave,' he wrote after the experienced caver rubbished Musk's own plans to save the boys.

The Tesla boss and tech entrepreneur had previously offered to assist the rescue mission by building a miniature submarine.

But this idea was dismissed by 63-year-old Vernon Unsworth who accused Musk creating a 'PR stunt'.

Unsworth, who led parts of the operation, said Musk 'can stick his submarine where it hurts'.

Later, when challenged by a social media user, Musk refused to withdraw his groundless attack.

'Bet ya a signed dollar it's true,' he wrote.

'It just had absolutely no chance of working. He had no conception of what the cave passage was like' Mr Unsworth earlier told CNN.

'The submarine, I believe, was about five-foot-six long, rigid, so it wouldn't have gone round corners or round any obstacles.'

In a series of tweets responding to a journalist Musk said: 'Never saw this British expat guy who lives in Thailand at any point when we were in the caves. Only people in sight were the Thai navy/army guys, who were great. Thai navy seals escorted us in — total opposite of wanting us to leave.

'Water level was actually very low & still (not flowing) — you could literally have swum to Cave 5 with no gear, which is obv how the kids got in. If not true, then I challenge this dude to show final rescue video. Huge credit to pump & generator team. Unsung heroes here.

'You know what, don't bother showing the video. We will make one of the mini-sub/pod going all the way to Cave 5 no problemo.'

Mr Unsworth knows the Tham Luang cave system where the boys were trapped very well, as he has spent years exploring it.

Musk was mocked online after the boys were rescued without the aid of his submarine - but he has hit back at critics and said the dive teams encouraged him to continue the work.

Photos released by The Chiang Rai Hospital showing boys that have been recused from caves in Northern Thiland

Musk earlier tweeted a screenshot of an email from Richard Stanton, who co-led the dive rescue team, asking him to keep working on the submarine.

He said that 'former provincial governor' Narongsak Osottanakorn had been wrongly described as the 'rescue chief', adding that Osottanakorn - the man who rejected his sub - is no expert in cave rescue.

The actual expert, according to Musk, is a man by the name of Richard Stanton who encouraged him to build the submarine, saying it 'may well be used'.

Musk took aim at Osottanakorn in a barbed tweet on Tuesday afternoon in which he downplayed his role in the rescue and suggested a man named Dick Stanton was the expert

The billionaire then shared what he claimed was a transcript of his emails with Stanton in which the diver encourages him to build the sub, saying 'it may well be used'

But he adds: 'I don't want to put it on a plane if you think important changes are needed.'

Musk claims Stanton responds: 'It is absolutely worth continuing with the development of this system in as timely a manner as feasible. If the rain holds out it may well be used.'

Elon answers: 'Right now, I have one [of] the world's best engineering teams who normally design spacesuits working on this 24 hours a day.

'We are trying to get it right in a very short period of time.

Musk also shared images of the camp which has been established around the cave mouth

The tech billionaire also tweeted images from inside the cave as rescuers attempted to save the final four boys and their 25-year-old coach who is still trapped

Musk was pictured meeting with Thai rescuers despite his offer of help being turned down

'If it isn't needed or won't help, that would be great to know. Otherwise, it would be very helpful to have as much design direction as possible.'

Musk also took to Twitter to bemoan being labelled a billionaire in reports about his involvement in the rescue - despite the fact he's worth £15billion.

'Ironically, the 'billionaire' label, when used by media, is almost always meant to devalue & denigrate the subject' he said.

'I wasn't called that until my companies got to a certain size, but reality is that I still do the same science & engineering as before. Just the scale has changed.'

It comes as Musk denies being a top donor to a PAC aimed at keeping Republican control of US Congress - despite being listed on the Federal Election Commission's website as being so.

'Reports that I am a top donor to GOP are categorically false. I am not a top donor to any political party,' he tweeted Saturday, following The Hill's report on the annual fillings released by the FEC this week.

The FEC shows Musk was among the top 50 donors to the Protect The House, Political Action Committee (PAC) giving a total of $38,900.

The sum is modest in comparison to other donors in the FEC filings. Microsoft co-founder Paul Allen donated $100,000 to the PAC while Houston Texans owner Bob McNair gave $371,500.

Perhaps Musk is parsing words, being in the top 50 out of 350 people may not constitute a 'top donor' for Musk.

Writing on the social media site, he said: 'Ironically, the 'billionaire' label, when used by media, is almost always meant to devalue & denigrate the subject'