Billionaire Tesla CEO Elon Musk is leaving the Trump administration after leading a tumultuous efficiency drive during which he upended several federal agencies but failed to deliver the generational savings he had sought.

Musk took to his social media platform X to thank President Donald Trump as his time as a special government employee with the Department of Government Efficiency draws to an end.

“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,” he wrote.

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

A White House official, who requested anonymity to talk about the change, confirmed that Musk was leaving and his "off-boarding will begin tonight”.

Musk's departure comes one day after he criticised the centrepiece of Trump’s legislative agenda, saying he was “disappointed” by what the president calls his “big beautiful bill”.

Musk leaves Trump administration after turbulent effort to slash government. – AP

His departure was quick and unceremonious. He did not have a formal conversation with Trump before announcing his departure, according to a source with knowledge of the matter, who added that his exit was decided "at a senior staff level."

While the precise circumstances around his exit were not immediately clear, he leaves a day after criticizing the Trump's marquee tax bill, calling it too expensive and a measure that would undermine his work with the US DOGE Service.

Over the last several weeks, he had butted heads in private with some cabinet-level officials. He publicly attacked White House trade adviser Peter Navarroas for dismissing Musk's push for "zero tariffs" between the US and Europe.

The billionaire entrepreneur, who supported Trump's candidacy with at least $250 million and has worked for his administration as a senior adviser, said he was "disappointed" by what the president calls his "big beautiful bill."

The legislation includes a mix of tax cuts and enhanced immigration enforcement. While speaking to CBS, Musk described it as a "massive spending bill" that increases the federal deficit and "undermines the work" of his Department of Government Efficiency, known as 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."

His CBS interview aired May 27. Trump, speaking in the Oval Office on Wednesday, defended his agenda by talking about the delicate politics involved with negotiating the legislation.

Elon Musk is leaving the Trump administration after a turbulent effort to slash government spending. - AP

"I'm not happy about certain aspects of it, but I'm thrilled by other aspects of it," he said.

Trump also suggested that more changes could be made.

"We're going to see what happens," he said. "It's got a way to go."

Republicans recently pushed the measure through the House and are debating it in the Senate.

Musk's comments come as he steps back from his government work, rededicating himself to companies like the electric automaker Tesla and rocket manufacturer SpaceX. He's also said he'll reduce his political spending, because "I think I've done enough."

Elon Musk criticises Trump's 'big beautiful bill,' a fracture in a key relationship. – AP

At times, he's seemed chastened by his experience working in government. Although he hoped that DOGE would generate $1 trillion in spending cuts, he's fallen far short of that target.

"The federal bureaucracy situation is much worse than I realised," he told The Washington Post.

"I thought there were problems, but it sure is an uphill battle trying to improve things in DC, to say the least."

The White House is set to send proposed rescissions, a mechanism used to cancel previously authorised spending, to Capitol Hill to solidify some of DOGE's cuts.

A spokesperson for the Office of Management and Budget said the package will include $1.1 billion from the Corporation of Public Broadcasting, which funds NPR and PBS, and $8.3 billion in foreign assistance.

Musk had previously been energised by the opportunity to reshape Washington. He wore campaign hats in the White House, held his own campaign rallies and talked about excessive spending as an existential crisis.

He often tended to be effusive in his praise of Trump.

"The more I've gotten to know President Trump, the more I like the guy," Musk said in February. "Frankly, I love him."

Trump repaid the favour, describing Musk as "a truly great American." When Tesla faced declining sales, he turned the White House driveway into a makeshift showroom to illustrate his support.

It's unclear what, if any, impact that Musk's comments about the bill would have on the legislative debate. During the transition period, he helped whip up opposition to a spending measure as the country stood on the brink of a federal government shutdown.

Elon Musk and Donald Trump. – Reuters

Speaker Mike Johnson has asked senators to make as few changes to the legislation as possible, saying that House Republicans reached a "very delicate balance" that could be upended with major changes. The narrowly divided House will have to vote again on final passage once the Senate alters the bill.

However, Musk's criticism could embolden Republicans who want bigger spending cuts. The republican senator from Utah, Mike Lee, reposted a Fox News story about Musk's interview while also adding his own take on the measure, saying there was "still time to fix it."

"The Senate version will be more aggressive," Lee said. "It can, it must, and it will be. Or it won't pass."

Only two Republicans – Representatives Warren Davidson of Ohio and Thomas Massie of Kentucky – voted against the bill when the House took up the measure last week.

Davidson took note of Musk's comments on social media.

Elon Musk in Saudi Arabia during Donald Trump's tour there. – Reuters

"Hopefully, the Senate will succeed with the Big Beautiful Bill where the House missed the moment," he wrote.

"Don't hope someone else will cut deficits someday, know it has been done this Congress."

The Congressional Budget Office, in a preliminary estimate, said the tax provisions would increase federal deficits by $3.8 trillion over the decade, while the changes to Medicaid, food stamps and other services would reduce spending by slightly more than $1 trillion over the same period.

House Republican leaders say increased economic growth would allow the bill to be deficit neutral or reducing, but outside watchdogs are skeptical. The Committee for a Responsible Federal Budget estimates the bill would add $3 trillion to the debt, including interest, over the next decade.

DOGE goes on

Musk's 130-day mandate as a special government employee in the Trump administration was set to expire around May 30. The administration has said DOGE's efforts to restructure and shrink the federal government will continue.

Several cabinet secretaries are already discussing with the White House how to proceed without further alienating Congressional Republicans. But even as department heads will keep some DOGE infrastructure in place, they will likely move to reassert control over budgets and staffing, sources have said.

Trump and DOGE have managed to cut nearly 12%, or 260,000, of the 2.3 million-strong federal civilian workforce largely through threats of firings, buyouts and early retirement offers, a Reuters review of agency departures found.

At the same time, DOGE has hit a number of roadblocks, with federal courts at times propping back up agencies shortly after DOGE had moved to eliminate them. In some cases, staff and funding cuts have led to purchasing bottlenecks, increased costs and a brain drain of scientific and technological talent.

Musk, the world's richest person, has defended his role as an unelected official who was granted unprecedented authority by Trump to dismantle parts of the U.S. government.

Having spent nearly $300 million to back Trump's presidential campaign and other Republicans last year, he said earlier this month he would substantially cut his political spending.

"I think I've done enough," Musk said at an economic forum in Qatar.