Donald Trump has launched a scathing attack on the British government and its ambassador, a day after leaked diplomatic cables revealed him calling the Trump administration “dysfunctional” and “inept”.In an outburst remarkable even by the standards of the US president, who frequently has little time for the niceties of diplomatic protocol, Mr Trump said on Twitter the US would no longer deal with Sir Kim Darroch, who has served as British ambassador to Washington since January 2016. It was later reported he had been disinvited from an official dinner.“I have been very critical about the way the UK and prime minister Theresa May handled Brexit. What a mess she and her representatives have created. I told her how it should be done, but she decided to go another way,” he wrote.“I do not know the ambassador, but he is not liked or well thought of within the US. We will no longer deal with him.”He added: “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.”Britain, which has long treasured the so-called “special relationship” with the US, has been scrambling on how best to respond after the Mail on Sunday published the contents of leaked diplomatic cables sent by Sir Kim to officials at the Foreign and Commonwealth Office in London.In one cable, written in the period since Mr Trump’s inauguration in January 2017, Sir Kim wrote: “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.”The publication of the cables, which the British foreign office has confirmed as genuine, has created an embarrassing headache for London. Ms May has said she has full confidence in Sir Kim, even while stressing that while it was the ambassador’s job to provide “an honest and unvarnished view” of the US administration, she was not necessarily required to agree with everything he wrote.Liam Fox, the international trade secretary, who is meeting the president’s daughter, Ivanka Trump, in the US, said he would be apologising for the way “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 behaviour”.Responding to the tweets from Mr Trump, a Downing Street spokesperson said Mr Darroch continued to enjoy the prime minister’s full support. “We have made clear to the US how unfortunate this leak is. The selective extracts leaked do not reflect the closeness of, and the esteem in which we hold, the relationship,” they added. “At the same time we have also underlined the importance of ambassadors being able to provide honest, unvarnished assessments of the politics in their country. “The UK has a special and enduring relationship with the US based on our long history and commitment to shared values and that will continue to be the case.”The job of ambassador to Washington is probably the most senior posting for a diplomat from Britain, or any other country. While Britain would normally seek to resist having its choice of envoy dictated to it, its hand is somewhat weakened by current circumstances.Firstly, London may have initially expected Mr Trump to brush aside the matter. On Sunday, he appeared to do so when he told reporters: “We’ve had our little ins and outs with a couple of countries and I would say that the UK, and the ambassador has not served the UK well, I can tell you that.”He added: “We’re not big fans of that man and he has not served the UK well, so I can understand it.”On Monday, Bloomberg News reported Sir Kim had been disinvited from a dinner that treasury secretary Steven Mnuchin was hosting on Monday with Mr Trump and the emir of Qatar.The decision on whether to replace Sir Kim will not be that of Mr May for much longer. On 23 July, members of Britain’s Conservative Party will elect a new leader to replace Ms May, and in doing so appoint the next prime minister.Polls show former London mayor and foreign secretary Boris Johnson to be some way ahead of the current foreign secretary, Jeremy Hunt, in the two man showdown. Mr Trump, who has said he likes Mr Johnson and suggested he would make a good prime minister, has also said Nigel Farage, the leader of the Brexit Party, could be ambassador to Washington.Mr Farage is among those who have called for Sir Kim to be sacked. “From the moment Trump was elected this man was the wrong person to be the British ambassador – a globalist in outlook, totally opposed to the Trump doctrine,” he said.