The former UK ambassador to the US said that Trump left the Iran nuclear deal to spite Barack Obama, a new report claims.

Kim Darroch called the move "diplomatic vandalism" while he was still serving as the ambassador and said that the US appeared to have no follow-up strategy, the Mail on Sunday reported, citing leaked cables and briefing notes.

Darroch resigned earlier this month after leaked cables revealed that he had called Trump "inept" and "incompetent," and Trump in response called him a "very stupid guy" and a "pompous fool."

Trump left the 2015 Iran nuclear deal in 2018, claiming that the deal, which saw Iran agree to limit its sensitive nuclear activities in exchange for lifted economic sanctions, did not go far enough.

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The UK's former ambassador to the US reportedly said that US President Donald Trump abandoned the international deal intended to limit Iran's nuclear capabilities just to spite his predecessor Barack Obama, and called the move "diplomatic vandalism."

The UK's Mail on Sunday newspaper reported that Kim Darroch wrote made the comments in a May 2018 memo, when he was still serving as the ambassador.

The report said they were made when the UK's then-foreign minister, Boris Johnson, went to the White House in a fruitless bid to convince Trump to stay with the deal, which was negotiated by Obama.

"The Administration is set upon an act of diplomatic vandalism, seemingly for ideological and personality reasons – it was Obama's deal," Darroch wrote, the Mail on Sunday reported, citing leaked cables and briefing notes.

Read more: The UK ambassador to the US's leaked cables calling Trump 'insecure' cost him his job because they were accurate

"Moreover, they can't articulate any 'day-after' strategy; and contacts with State Department this morning suggest no sort of plan for reaching out to partners and allies, whether in Europe or the region."

Kim Darroch, then the UK's ambassador to the US, speaking in Washington. Niall Carson/PA Images via Getty Images

The report comes after Darroch's resignation in light of leaked diplomatic cables in which he called Trump "inept" and "incompetent," and called the Trump White House "uniquely dysfunctional."

Darroch resigned on July 10, saying that it had become "impossible" for him to remain in the role.

Read more: Kim Darroch resigns as UK ambassador to the US over leaked memos branding Trump 'incompetent'

"The current situation is making it impossible for me to carry out my role as I would like," he said.

Trump had attacked Darroch after the leak, calling him a "very stupid guy" and a "pompous fool" — though he later seemed to change his tone and said "I wish him well" after seeing a tweet that said Darroch had compared him to Arnold Schwarzenegger in "The Terminator."

The UK's Sunday Times newspaper reported that a suspect has been identified for the leaks, citing unnamed government sources.

Donald Trump holds up a copy of the memorandum he signed, enacting a US departure from the Iran deal. AP

The leaks have also rattled UK politics, as Johnson, now the frontrunner become the next prime minister, has come under fire for refusing to say that Darroch should keep his job. Another former UK ambassador to the US accused Johnson of being "a fully paid up member of the Donald Trump fan club."

Trump had criticized the Iran nuclear deal as not going far enough before he pulled out in 2018. The deal, signed by Iran, the EU, the US, China, Russia, and other states in 2015 after years of negotiations, saw Iran agree to limit its sensitive nuclear activities so that economic sanctions would be lifted.

The US has since reinstated sanctions against Iran, something Iran called "economic terrorism" in June.