Elon Musk has said he is leaving the Trump administration after helping lead a tumultuous drive to shrink the size of US government that saw thousands of federal jobs axed.

In a post on his social media platform X, the world's richest man thanked Trump for the opportunity to help run the Department of Government Efficiency, known as Doge.

The White House began "offboarding" Musk as a special government employee on Wednesday night, the BBC understands.

His role was temporary and his exit is not unexpected, but it comes a day after Musk criticised the legislative centrepiece of Trump's agenda.

"As my scheduled time as a Special Government Employee comes to an end, I would like to thank President @realDonaldTrump for the opportunity to reduce wasteful spending," Musk wrote on X.

"The @DOGE mission will only strengthen over time as it becomes a way of life throughout the government."

The South African-born tech tycoon had been designated as a "special government employee" - allowing him to work a federal job for 130 days each year.

Measured from Trump's inauguration on 20 January, he would hit that limit towards the end of May.

But his departure comes a day after he said he was "disappointed" with Trump's budget bill, which proposes multi-trillion dollar tax breaks and a boost to defence spending.

The SpaceX and Tesla boss said in an interview with BBC's US partner CBS that the "big, beautiful bill", as Trump calls it, would increase the federal deficit.

Musk also said he thought it "undermines the work" of Doge.

"I think a bill can be big or it could be beautiful," Musk said. "But I don't know if it could be both."

Musk, who had clashed in private with some Trump cabinet-level officials, initially pledged to cut "at least $2 trillion" from the federal government budget, before halving this target, then reducing it to $150bn.

An estimated 260,000 out of the 2.3 million-strong federal civilian workforce have had their jobs cut or accepted redundancy deals as a result of Doge.

In some cases, federal judges blocked the mass firings and ordered terminated employees to be reinstated.

The rapid-fire approach to cutting the federal workforce occasionally led to some workers mistakenly being let go, including staff at the US nuclear programme.

Musk announced in late April that he would step back to run his companies again after becoming a lightning rod for criticism of Trump's efforts to shake up Washington.

"Doge is just becoming the whipping boy for everything," Musk told the Washington Post in Texas on Tuesday ahead of a Space X launch.

"Something bad would happen anywhere, and we would get blamed for it even if we had nothing to do with it."

Musk's time in government overlapped with a significant decline in sales at his electric car company.

Tesla sales dropped by 13% in the first three months of this year, the largest drop in deliveries in its history.

The company's stock price also tumbled by as much as 45%, but has mostly rebounded and is only down 10%.

Tesla recently warned investors that the financial pain could continue, declining to offer a growth forecast while saying "changing political sentiment" could meaningfully hurt demand for the vehicles.

Musk told investors on an earnings call last month that the time he allocates to Doge "will drop significantly" and that he would be "allocating far more of my time to Tesla".

Activists have called for Tesla boycotts, staging protests outside Tesla dealerships, and vandalising the vehicles and charging stations.

The Tesla blowback became so violent and widespread that US Attorney General Pam Bondi warned her office would treat acts of vandalism as "domestic terrorism".

Speaking at an economic forum in Doha, Qatar, on Tuesday, Musk said he was committed to being the leader of Tesla for the next five years.

He said earlier this month he would cut back his political donations after spending nearly $300m to back Trump's presidential campaign and other Republicans last year.