Elon Musk has criticised one of the signature policies of Donald Trump, marking a break from the US president who he helped to win re-election in 2024.

Last week, the US House of Representatives narrowly passed what Trump calls his "big, beautiful" bill, which includes multi-trillion dollar tax breaks and a pledge to increase defence spending. It will now head to the Senate.

Tech titan Musk told the BBC's US partner CBS News he was "disappointed" by the plan, which he felt "undermines" the work he did for the president on reducing spending.

Musk was enlisted as Trump's cost-cutting tsar - ending funds for US foreign aid among other projects - before announcing he would step back.

"I was disappointed to see the massive spending bill, frankly," Musk said in the interview with CBS Sunday Morning, a clip of which was released by the broadcaster before transmission.

He went on to argue that Trump's plan "increases the budget deficit, not just decreases it".

It is thought that the legislation could increase the deficit - or the difference between what the US government spends and the revenue that it receives - by about $600bn (£444bn) in the next fiscal year.

Furthermore, the bill "undermines the work that the Doge team is doing", Musk said, using the acronym of the cost-cutting advisory body the Department of Government Efficiency.

Referring to Trump's moniker for the legislation, Musk told CBS: "I think a bill can be big or beautiful. I don't know if it can be both."

Musk's intervention highlights the ongoing tension within Trump's Republican Party over the tax-and-spend plans, which faced an uneasy passage through the House due to opposition from different wings of the party.

Speaking to reporters in the Oval Office on Wednesday, Trump acknowledged that he is "not happy about certain aspects" of the bill while at the same time being "thrilled" about some aspects, such as tax cuts.

"It's the big, beautiful bill," he said. "And it's beautiful because of all the things we have."

When asked, Trump did not directly comment on Musk's remarks.

Long a policy priority of Trump's, the legislation pledges to extend soon-to-expire tax cuts passed during his first administration in 2017, as well as provide an influx of money for defence spending and to fund the president's mass deportations.

The bill also proposes increasing to $4tn the debt ceiling - meaning the limit on the amount of money the government can borrow to pay its bills.

Musk's comments on the issue imply a growing distance from Trump, who he helped to propel back to the White House last year with donations of more than $250m.

They come after the billionaire recently pledged to step back from Doge. Musk had stated that he wanted to help the government cut $1tn in spending by cancelling contracts and reducing the government workforce.

As of April, Doge's website claims around $175bn has already been saved, but a BBC analysis of this figure shows it lacks some evidence.

Musk also said last week that he planned to do "a lot less" political spending in the future, and that he was committed to leading electric car company Tesla for another five years.

Tesla faced protests, boycotts and a drop in sales over Musk's work as the Doge chief, including his controversial efforts to lay off thousands of federal workers and curb foreign aid.

Musk defended his actions in his comments last week, saying: "I did what needed to be done." He and Trump previously justified the cuts as a matter of weeding out what they saw as fraud and abuse within federal spending.