LONDON — In an angry broadside against one of America's closest allies, President Donald Trump said he would "no longer deal" with the British ambassador to the U.S. following an embarrassing diplomatic leak.

"I do not know the ambassador, but he is not liked or well thought of within the U.S.," Trump tweeted of the ambassador, Kim Darroch. "We will no longer deal with him."

Trump also lashed out at outgoing Prime Minister Theresa May.

....thought of within the U.S. We will no longer deal with him. The good news for the wonderful United Kingdom is that they will soon have a new Prime Minister. While I thoroughly enjoyed the magnificent State Visit last month, it was the Queen who I was most impressed with! — Donald J. Trump (@realDonaldTrump) July 8, 2019

"I have been very critical about the way the U.K. and Prime Minister Theresa May handled Brexit," Trump wrote. "What a mess she and her representatives have created. I told her how it should be done, but she decided to go another way."

These scathing comments followed attempts by British officials' to stem the spat that threatened to complicate Anglo-U.S. relations at a time when the United Kingdom needs the White House's support.

It was revealed Sunday that Britain’s top diplomat in the United States had described Trump as “inept” and “insecure,” and dismissed his administration as “dysfunctional” and “faction ridden” in a series of cables to London.

Foreign Secretary Jeremy Hunt, who is vying to be Britain’s next prime minister, said Darroch had expressed his “personal view,” while making clear he did not share the envoy's opinions.

“I think the U.S. administration is highly effective and we have the warmest of relationships and a partnership based on standing up for shared values,” Hunt told reporters Monday.

The weekend revelations came as Britain struggles to leave the European Union and is in the midst of the ruling Conservative Party's leadership race. The U.K. hopes to look beyond Brussels for future trade deals and close relations, and many see a U.S. deal as a pillar of a post-E.U. Britain.

Trade Minister Liam Fox who is on a visit to Washington said he would apologize to the president's daughter Ivanka Trump, whom he is due to meet during his trip.

It’s embarrassing but I think the embarrassment will blow over.

"Malicious leaks of this nature are unprofessional, unethical and unpatriotic and can actually lead to a damage to that relationship, which can therefore affect our wider security interest," he told BBC News on Monday.

The British government is investigating who was the source of the leak.

“We believe the leak is unacceptable,” May’s spokesman told reporters Monday.

Despite the countries' oft-touted special relationship, ties between Washington and Westminster have seen some strains throughout Trump's presidency. For example, the president has previously criticized May's handling of Brexit and has praised her likely successor, Boris Johnson.

While the memos were critical of Trump, the leak is actually a headache for Britain, according to Jonathan Eyal, associate director at the Royal United Services Institute, a think tank in London.

The content of the memos was "not exactly remarkable stuff," Eyal said.

"The market had already priced these things in" and the criticism was unlikely to change the minds of Trump supporters or critics, he added.

The leak was a thornier issue for Britain, however, as it comes soon after a state visit, weeks before a new government will take office and months ahead of the end of Darroch’s term in Washington — raising the question of who should replace him, Eyal said.

Darroch is a veteran diplomat who is into his third year of what is usually a four-year posting.

“There is a feeling [in London] that has existed for a while that the Trump presidency is so unusual, different from that of his predecessors, that only someone with political clout rather than diplomatic clout will do,” he said, cautioning that he thought this was the wrong approach.

From the start of his presidency, Trump has called on Britain to appoint a person he trusts as ambassador to Washington, Eyal said.

In 2016, Trump said Brexit Party leader Nigel Farage would do a “great job” as ambassador to the U.S. The pair have met on several occasions, most recently in London during last month’s state visit.

Farage responded to the leaked cables on Monday, saying Darroch was “totally unsuitable” for the job.

Writing in The Daily Telegraph, the Brexit campaigner said he thought that if Conservative Party front-runner Johnson becomes prime minister later this month “Darroch’s time in Washington will draw to a close.”

However, when asked if he would accept the post of ambassador to the U.S. if offered it, Farage told BBC News that he didn’t think he was the “right man for the job.”

Richard Dalton, a former British ambassador to Iran, said a useful parallel could be drawn between this weekend's leak and the diplomatic cables published by Wikileaks in 2010.

The Wikileaks files also contained damaging implications for Britain and the so-called special relationship, but in the end, Dalton said, national interests overcame the diplomatic blip. He believed the same would happen in this case.

“I don’t see it being gravely damaging. It’s embarrassing but I think the embarrassment will blow over,” he told NBC News.