By Alan McGuinness, political reporter
Jeremy Hunt has warned there will be "serious consequences" for whoever is responsible for leaking memos from the UK's ambassador to Washington, as Downing Street said Theresa May has "full confidence" in Sir Kim Darroch.
Mr Hunt, the foreign secretary, said the disclosure of notes from Sir Kim "fundamentally undermines" the work of British diplomats around the world and was "not acceptable".
In the memos, obtained by The Mail On Sunday, Sir Kim described Donald Trump as "incompetent", "inept" and "insecure".
He said the White House under America's 45th president had become "uniquely dysfunctional" because of "vicious infighting and chaos", and questioned whether it "will ever look competent".
Mr Trump hit back, saying the ambassador "has not served the UK well", while the leak has inevitably caused controversy on the other side of the Atlantic as well.
Asked about the disclosure at a press conference at the Foreign Office, Mr Hunt said Sir Kim's assessment was a "personal view" of the state of US politics and that he was doing his job as an ambassador.
"I don't share the ambassador's assessment of either the US administration or relations with the US administration, but I do defend his right to make that frank assessment and it's very important that our diplomats all over the world continue to be able to do so," Mr Hunt said.
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The Tory leadership contender continued: "I'm very concerned about it [the leak], because fundamental to the proper functioning of our diplomatic network, which I happen to believe is one of the finest if not the finest in the world, is to be able to exchange opinions frankly.
"So we need to find out how it happened, not least to give confidence to our teams all over the world that they can continue to give us their frank assessment.
"So that's why we're going to have a leak inquiry. I hope we get to the bottom of it.
"Of course there'll be very serious consequences if and when we find out whoever is responsible."
Downing Street has said Prime Minister Theresa May has "full faith" in Sir Kim but does not agree with all of his assessment of the Trump White House.
"Our ambassadors provide honest, unvarnished assessments of politics in their country – those views are not necessarily the views of ministers or indeed of the government, the PM's official spokesman said.
"As the Foreign Secretary has said, this leak is not acceptable.
"We would expect such advice to be handled in the correct way and a leak inquiry has been launched."
Number 10 said officials have been in touch with the Trump administration and told Washington they believe the leak is "unacceptable".
As the investigation gets under way, there have already been calls for tough action against whoever is responsible.
Former defence secretary Sir Michael Fallon told Sky News the leak was "clearly a breach of the Official Secrets Act" and if whoever is responsible can be identified then "prosecutions should follow".
Sir Michael, who is backing Boris Johnson to be the next Tory leader and prime minister, added that Mr Johnson has a "very good relationship" with Mr Trump and can "smooth over any particular hurt that the president feels about this and to get that relationship back on track".
Sir Mark Lyall Grant, former UK ambassador to the UN, told Sky's All Out Politics that he thought it was a "malicious leak" that was "almost certainly" a "politically motivated one".
He added: "And that I Read More – Source[contf] [contfnew]