In the highly sensitive documents, Sir Kim described the White House as “incompetent” and “inept”, writing: “We don’t really believe this administration is going to become substantially more normal.”
Speaking to reporters in New Jersey on Sunday, Mr Trump said: “The ambassador has not served the UK well, I can tell you that.” He added: “We are not big fans of that man and he has not served the UK well ... I can say things about him but I won’t bother.”
The UK government said earlier today that it had launched an investigation to discover who leaked the memos, while the Foreign Office stated: “Our team in Washington have strong relations with the White House and no doubt ... these will withstand such mischievous behaviour.”
The British embassy informed the White House on Friday that the memos would be published over the weekend, according to a person familiar with the matter, and the two sides were in touch throughout the weekend.
UK justice secretary David Gauke called the leak “disgraceful” but said Britain “should expect our ambassadors to tell the truth, as they see it.”
Foreign secretary Jeremy Hunt moved to prevent damage caused by the disclosure of candid cables, describing the comments as “personal opinions” and “not the opinions of the British government”.
Mr Hunt said on Sunday: “It’s really important to say that the ambassador was doing his job as an ambassador which is to give frank reports and personal opinions about what’s happening in the country where he works, and that’s his job to send back those reports but they are personal opinions, not the opinions of the British government, not my opinion.
“And we continue to think that under President Trump the United States administration is both highly effective and the best possible friend of Britain on the international stage.”
The memos characterised Mr Trump’s policy on Iran as “incoherent, chaotic.” The president has frustrated European allies by withdrawing the US from a complex deal designed to prevent Tehran from obtaining nuclear weapons and has seemed in recent weeks to be on the verge of armed conflict with Iran.
The British ambassador said he did not believe Mr Trump’s public explanation for calling off a planned military strike against Iran last month because of concern about possible civilian casualties. Sir Kim said it was more likely the strike was cancelled because he felt it would be a liability in the upcoming 2020 presidential election.
Speaking to reporters on Sunday as he departed Morristown for Washington, Mr Trump said Iran “better be careful,” hours after Tehran announced it would shortly boost its uranium enrichment above a cap set by a landmark 2015 nuclear deal.
In one of the memos, Sir Kim warned British officials not to write the president off, saying there was a “credible path” to him winning a second term. He said Mr Trump may “emerge from the flames, battered but intact, like [Arnold] Schwarzenegger in the final scenes of The Terminator.”