After days of wide criticism, Elon Musk has apologised for calling Vernon Unsworth, one of the Thai cave rescue divers, a "pedo guy."

"My words were spoken in anger after Mr. Unsworth said several untruths & suggested I engage in a sexual act with the mini-sub," he tweeted late Tuesday night. "Nonetheless, his actions against me do not justify my actions against him, and for that I apologize to Mr. Unsworth and to the companies I represent as leader. The fault is mine and mine alone."

In a Sunday tweet, Musk had labeled Unsworth, a diver who helped rescue 12 boys and their soccer coach from a flooded cave, a "pedo guy", after Unsworth criticised a submarine rescue plan the billionaire had proposed. The tweet has since been deleted. 

Musk was criticised heavily following the tweet, with backlash even coming from Tesla investors.

Unsworth on Sunday called Musk's involvement a "PR stunt," telling CNN his submarine wouldn't have made it 50 metres into the cave.

"He can stick his submarine where it hurts," he said, which is the sexual act Musk's apology tweet refers to. "It just had no chance of working." These comments are what triggered Musk's subsequent tweets.

"We will make [a video] of the min-sub/pod going all the way to Cave 5 no problemo. Sorry pedo guy, you really did ask for it," one of his now-deleted tweets read.

On Monday, Unsworth told AFP that he was considering legal action against Musk.

The Tesla and SpaceX CEO was reprimanded by Tesla investors in an open letter on Tuesday. Gene Munster, a managing partner at Loup Ventures, said Musk's comment "crossed the line."

"Your behavior is fueling an unhelpful perception of your leadership -- thin-skinned and short-tempered," Munster wrote in his letter, which was published on behalf of investors. "I suspect you would agree, given you removed the string from Twitter, but it will take more than that to regain investor confidence."

In the letter, investors urge Musk to apologize, then "focus your message on your progress toward achieving Tesla's mission." That could even involve a Twitter sabbatical, they suggest.

It's the latest instance of mounting scrutiny toward Musk. Earlier this month, he criticized the media for "negative" coverage of Tesla, and in May said he would create a site where people could rate the trustworthiness of an article and track journalists' "credibility score." There have also been larger issues involving Tesla, the electric car company having dealt with scandals involving worker injuries and fatal crashes.

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