US President Donald Trump has heaped praise on Elon Musk at a press conference in the Oval Office marking the billionaire Tesla’s chief’s departure.

Musk’s chaotic role spearing the Department of Government Efficiency (DOGE) came to an end on Saturday (AEST).

The world’s richest man and Trump wingman controversially eliminated thousands of jobs and cut billions of dollars in contracts.

But despite disrupting numerous agencies across the federal bureaucracy he ultimately fell far short of the massive savings, he had initially promised.

Trump said he suspected Musk “is really not leaving” and would still be going “back and forth” to the White House.

“Elon has worked tirelessly helping lead the most sweeping and consequential government reform program in generations,” said Trump.

Musk stood to the president’s right wearing a black DOGE hat and a t-shirt that read “The Dogefather” in the style of the movie “The Godfather.”

He was also sporting a visible black eye, which he later explained had been caused by his five-year-old son after he invited him to punch him in the face.

“I was walking around with Little X and I said, ‘Go ahead and punch me in the face,’ and he did,” Musk claimed.

“I didn’t really feel much at the time but I guess it bruises up.”

Musk said he would continue to serve as a Trump adviser and expressed confidence that DOGE would eventually achieve much deeper savings.

“This is not the end of DOGE but really the beginning,” he said.

The farewell formality was overshadowed by a bombshell report claiming Musk was allegedly taking a variety of drugs — such as ketamine, ecstasy and psychedelic mushrooms — while advising Trump.

The report in the New York Times claims that Musk travelled with a daily supply of about 20 pills, including ADHD medication Adderall.

His drug use was reportedly traced to 2024 when Musk donated $275 million to Trump’s presidential campaign; however it was not known if it continued after Trump moved into the White House.

The New York Times says Musk’s consumption of ketamine was a “daily” habit — rather than once every two weeks to treat depression as he had claimed — and led to the world’s richest man having bladder problems.

When asked about the report, Musk hit back at the New York Times.

“Is that the same publication that got a Pulitzer Prize for false reporting on the Russiagate? Is it the same organisation? I think it is!” he said.

“I think the judge just ruled against the New York Times for their lies about the Russiagate hoax, and that they might have to give back that Pulitzer Prize.”

President Donald Trump was full of praise for Elon Musk. Photo: AAP

White House spokesperson Harrison Fields did not respond directly to the drug claims.

He said Musk had accomplished “more for American taxpayers than many career politicians”.

“Few CEOs in America would leave the comfort of the C-suite to serve in the federal government,” Fields said in a statement.

“Yet Elon Musk did just that, joining the Trump Administration’s efforts to cut waste, fraud and abuse.

“DOGE and its core mission is now embedded in the fabric of the federal government and continues to drive efficiency and save taxpayer dollars.”

Musk announced he was stepping down from his White House stint on Thursday (AEST), giving Tesla investors some succour after shares slumped this year in part due to the backlash to his support of Trump and right-wing parties in Europe.

A day earlier, Musk had prompted some frustration among White House officials by criticising Trump’s sweeping tax and spending bill as too expensive.

Some senior aides, including Deputy Chief of Staff Stephen Miller and Chief of Staff Susie Wiles, saw Musk’s remarks on the tax bill as an open break from the administration, with Miller particularly irked by the comments.

There was no evidence of tension during the joint appearance on Friday, where Trump said Musk would continue to play a role in his administration.

In addition, Musk had recently pledged to spend less money on politics after he plunked down nearly $US300 million on Trump’s presidential campaign and on other Republican candidates last year.

A former DOGE staffer said without Musk in the Trump administration, his cost-cutting Department of Government Efficiency project is likely to sputter out.

Software engineer Sahil Lavingia, who spent almost two months working for the group of pro-Musk technologists, said he expects DOGE to quickly “fizzle out.”

“It’ll just die a whimper,” Lavingia, who was fired from DOGE earlier this month, told Reuters.

“So much of the appeal and allure was Elon.”

He said he expected DOGE staffers to “just stop showing up to work. It’s like kids joining a startup that will go out of business in four months.”

That would cap a remarkable undoing for DOGE, which Musk initially vowed would cut $US2 trillion in federal spending.

Instead, DOGE estimates its efforts have saved around $US175 billion so far and the group’s tallies have been riddled with errors.

Initially, the White House and senior aides insisted Musk, the world’s richest man, was a key figure who wasn’t going anywhere. 

But more recently, they began pointing to the expiration of his 130-day mandate as a special government employee, which was set to end around May 30, as a natural endpoint.

Musk has said he intends to devote most of his energy to his business empire, including Tesla and SpaceX, after some investors expressed concern that DOGE was occupying too much of his time.

US Treasury summaries reviewed by Reuters show that the agencies targeted by DOGE have cut about $US19 billion ($30 billion) in combined spending compared to the same period last year, far below Musk’s original target and amounting to just about 0.5 per cent of total federal expenditures.

-with AAP