Elon Musk has encouraged others to “free the nip” after his pasty physique was mocked online as pictures emerged from his recent holiday to Greece.

A shirtless Mr Musk soaked up the sun aboard a luxury yacht in Mykonos last weekend, with pictures of the multibillionaire’s holiday spreading across social media and international news outlets on Wednesday.

The Tesla founder, 51, responded to the uproar on Twitter, posting a reference to the equality movement #freethenipple.

Mr Musk enjoyed a few days aboard a $US20,000-a-week ($29,000) yacht called Zeus last the weekend with newlywed friends fashion designer Sarah Staudinger and entertainment and media boss Ari Emanuel.

By the time the pictures and the criticism emerged, however, he was apparently “already back in the factory”.

“Haha damn, maybe I should take off my shirt more often … free the nip!! (already back in the factory btw),” he tweeted in response to one of the thousands of posts about his recent getaway.

The world’s richest person also laughed off one unkind comparison between him and a small white dog standing on its hind legs.

“My calves are bigger tho (sic),” he wrote.

Mr Musk’s response to the criticism of his physique came hours after Twitter won the first legal skirmish in its attempt to force him to complete his $US44 billion ($64 billion) takeover of the social media company.

A Delaware judge ruled that a trial will go ahead in October, saying Twitter deserved a quick resolution of the deal’s uncertainty.

The ruling is a blow to Mr Musk, who wanted the trial delayed until February to allow for an extensive investigation into his claims that Twitter had misrepresented the number of fake or spam accounts.

Twitter had argued that delaying the trial into the next year could threaten deal financing.

Mr Musk, who is also the boss of private space exploration company SpaceX, has not responded to the expedition of the trial.

He had previously argued an expedited trial would allow Twitter to hide the truth about spam accounts, which Mr Musk began questioning after signing the deal for Twitter in late April.