Britain's ambassador to U.S. Darroch listens during Trump-May joint news conference at the White House in Washington
FILE - Britain's ambassador to the U.S. Kim Darroch listens as U.S. President Donald Trump and British Prime Minister Theresa May hold a joint news conference at the White House in Washington.

WASHINGTON - U.S. President Donald Trump on Tuesday called British ambassador Kim Darroch "a very stupid guy," a new taunt aimed at undercutting the envoy's assessment that Trump is "inept" and "incompetent."

"The wacky Ambassador that the U.K. foisted upon the United States is not someone we are thrilled with," Trump said on Twitter.

The U.S. leader said Darroch, Britain's top diplomat in Washington since 2016, "should speak to his country, and Prime Minister [Theresa] May, about their failed Brexit negotiation, and not be upset with my criticism of how badly it was handled. I told @theresa_may how to do that deal, but she went her own foolish way-was unable to get it done. A disaster!"

Trump added, "I don’t know the Ambassador but have been told he is a pompous fool. Tell him the USA now has the best Economy & Military anywhere in the World, by far."

Within hours, British Foreign Secretary Jeremy Hunt rebuked Trump, telling him that his comments about May and Britain were "disrespectful and wrong." Hunt said that if he becomes the British prime minister when May leaves office at the end of the month, he will retain Darroch as ambassador to Washington.

Hunt said U.S. diplomats stationed overseas "give their private opinions" to Secretary of State Mike Pompeo, just as British envoys report back to London. "But allies need to treat each other with respect" as May "has always done with you."

Trump on Monday said he would "no longer deal" with Darroch, claiming "he is not liked or well thought of within the U.S."

Later in the day, a White House official confirmed reports that Darroch was uninvited from a dinner that U.S. Treasury Secretary Steven Mnuchin was hosting with Trump and the emir of Qatar.

In this Friday, Oct. 20, 2017 photo, British Ambassador Kim Darroch hosts a National Economists Club event at the British Embassy in Washington. Leaked diplomatic cables published Sunday, July 7,2 019, in a British newspaper reveal that Britain's…
FILE - British Ambassador Kim Darroch hosts a National Economists Club event at the British Embassy in Washington, Oct. 20, 2017.

Meanwhile, Britain was scrambling to find the source of a leak of Darroch's diplomatic cables from Washington back to his homeland.

London, long the U.S.'s closest ally, was embarrassed by the disclosure of the unflattering assessments of Trump, but did not deny their accuracy after they were published in Britain over the weekend. 

May's spokesman, James Slack, told reporters, "Contact has been made with the Trump administration, setting out our view that we believe the leak is unacceptable. It is, of course, a matter of regret that this has happened."

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Trade Minister Liam Fox, who is visiting Washington, told BBC radio that he would apologize to Ivanka Trump, the president's daughter and one of his advisers.

"I will be apologizing for the fact that either our civil service or elements of our political class have not lived up to the expectations that either we have or the United States has about their behavior, which in this particular case has lapsed in a most extraordinary and unacceptable way," he said. "Malicious leaks of this nature ... can actually lead to a damage to that relationship, which can therefore affect our wider security interest."

The leaked cables were intended for the eyes of senior British ministers and civil servants, but officials believe the leaker will be found among British politicians or officials, not a foreign government.

It is possible the leaker could be charged with violating the country's Official Secrets Act, which bars disclosure of classified material, although prosecutions are rare.

Britain's Prime Minister Theresa May and U.S. President Donald Trump attend a joint news conference at the Foreign & Commonwealth Office, in London, Britain, June 4, 2019.
FILE - Britain's Prime Minister Theresa May and U.S. President Donald Trump attend a joint news conference at the Foreign & Commonwealth Office, in London, Britain, June 4, 2019.

Slack said May had "full faith" in Darroch, but did not agree with his assessment of Trump and his presidency. Slack said overseas envoys were hired to provide "honest, unvarnished assessments" of the politics and officials in the countries where they serve.

One of Darroch's cables, a collection from 2017 to recent weeks, said, "We don't really believe this administration is going to become substantially more normal; less dysfunctional; less unpredictable; less faction riven; less diplomatically clumsy and inept."

After first learning of Darroch's comments, Trump said the ambassador "has not served the U.K. well, I can tell you that. We are not big fans of that man."