Billionaire Elon Musk has said he will move the headquarters of two of his most high-profile companies, rocket firm SpaceX and social media platform X, out of California to Texas.

He cited his opposition to a new Californian state law which bans schools from requiring staff to disclose information about a child's gender identity - including to parents.

"This is the last straw," he wrote on social media.

The businessman had already moved Tesla's headquarters to Texas in 2021, a move he first threatened over Covid-era lockdowns.

Since then, he has become increasingly involved in US politics.

Over the weekend, he formally endorsed Donald Trump for president. On Tuesday, the Wall Street Journal reported he would be directing $45m a month toward his campaign. Mr Musk replied on Twitter/X with a picture of "fake gnus".

The issue of what schools should tell parents about their children's gender identities has become a major topic of debate in the US.

LGBTQ advocates say students have a right to privacy, but others argue parents have a right to know what is happening with their children.

Mr Musk, who has a transgender daughter, has previously said he "supports trans" while expressing impatience with pronouns, which he has described as an "aesthetic nightmare".

Last year, he said he would lobby to criminalise transgender medical treatment that would lead to what he described as "severe, irreversible changes to children below the age of consent".

"Because of this law and the many others that preceded it, attacking both families and companies, SpaceX will now move its HQ from Hawthorne, California, to Starbase, Texas," he said in a post on X on Tuesday, noting that he had previously expressed his opposition to the bill.

In explaining the decision to move X to Austin, Mr Musk criticised the state of affairs in San Francisco, saying he had "had enough of dodging gangs of violent drug addicts just to get in and out of the building".

California Governor Gavin Newsom, whose name is among the ones that have been floated to possibly replace President Joe Biden as the Democratic candidate for the upcoming election, took to social media in an apparent criticism of Mr Musk's decision.

“You bent the knee,” Mr Newsom posted, along with a screenshot of a 2022 post from Donald Trump criticising the billionaire.

A spokesperson for the governor said after the bill was signed that it kept "children safe while protecting the critical role of parents".

"It protects the child-parent relationship by preventing politicians and school staff from inappropriately intervening in family matters and attempting to control if, when, and how families have deeply personal conversations," Brandon Richards told the Associated Press.

States have historically competed aggressively to woo companies to establish headquarters, bringing with them high-paying corporate jobs.

Mr Musk himself is already a resident of Texas, which has no income tax.

SpaceX, which employs more than 5,000 people in California, according to state records, also already has a large base of operations in the state.

In response to Mr Musk's pledge, Greg Abbott, governor for Texas, said: "This cements Texas as the leader in space exploration."

Neither SpaceX nor X responded to requests for comment about whether the decision to move headquarters would lead to job cuts in California.