Donald Trump has been accused of disrespecting the UK and the Prime Minister after a Twitter tirade about her “foolish” leadership.

The US President dramatically stepped up the war of words following the leak of sensitive diplomatic messages from the UK’s ambassador to Washington painting a critical picture of the Trump White House.

Mr Trump called ambassador Sir Kim Darroch a “pompous fool” and a “very stupid guy” who had been foisted on the US.

In an extraordinary onslaught against an ally, Mr Trump also used a Twitter post to  attack Theresa May over Brexit, accusing her of ignoring his advice and “going her own foolish way”.

Foreign Secretary Jeremy Hunt shot back, using Mr Trump’s favoured social media platform to accuse the president of being “disrespectful and wrong”.

The Tory leadership hopeful said he would keep Sir Kim in post if he became prime minister.

In his explosive Twitter comments, Mr Trump said: “The wacky ambassador that the UK foisted upon the United States is not someone we are thrilled with, a very stupid guy.

“He should speak to his country, and Prime Minister 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!

“I don’t know the ambassador but have been told he is a pompous fool.”

Mrs May has made clear her full support for Sir Kim following the leak of diplomatic dispatches in which he described the White House as “inept” and “dysfunctional”.

Downing Street said Sir Kim remained in post after Mr Trump warned on Monday the White House would have nothing more to do with him.

The first indication of that became evident when the ambassador was “uninvited” to a White House dinner on Monday evening, held in honour of the Emir of Qatar.

Sir Kim was also not attending a meeting between Ivanka Trump and the International Trade Secretary Liam Fox in Washington.

The issue was discussed at Cabinet, where Mrs May denounced the leak of Sir Kim’s dispatches as “unacceptable” and stressed it was important ambassadors were able to provide “honest, unvarnished” advice to ministers.

Mr Trump’s outspoken attack, the most strident public criticism of a British prime minister by a US president in decades, caused dismay in Whitehall.

It comes just a month after the Government rolled out the red carpet for the president for a state visit in which he praised the enduring strength of the “special relationship”.

A formal civil service leak inquiry has been launched, but MPs called for the police to investigate.

The Foreign Affairs Committee, which will hear from senior Foreign Office mandarin Sir Simon McDonald on Wednesday, has written to the Prime Minister, Foreign Secretary and Metropolitan Police Commissioner Cressida Dick about the leak.

In his letter to Scotland Yard calling for a police investigation, committee chairman Tom Tugendhat said: “This appears to be a serious criminal act.”

In response to questions about Mr Trump’s comments, former foreign secretary and Tory leadership frontrunner Boris Johnson said:  “I have got a good relationship with the White House and I have no embarrassment in saying that.

“I think it’s very important that we have a strong relationship with our most important ally. The United States is, has been, will be and for the foreseeable future our number one political, military, friend.”

Asked whether the president was right to criticise Mrs May and the way Brexit talks have been handled, Mr Johnson replied: “I have said some pretty critical things about the Brexit negotiations so far and that’s one of the reasons I am standing tonight and one of the reasons I am putting myself forward.”

Senior figures lined up to insist the ministers were right to stand up for Sir Kim and warned the Government must not bow to US pressure.

Tory former foreign secretary Lord Hague told the BBC: “You can’t change an ambassador at the demand of a host country.”

Sir Christopher Meyer, former ambassador to the US, said Mr Trump’s reaction to the leak underlined the president’s “sensitivity” which Sir Kim had highlighted in his reports.

Sir Christopher said there was a “range of possible villains” who might have been responsible for passing his dispatches to the press.

“It was clearly somebody who set out, deliberately, to sabotage Sir Kim’s ambassadorship, to make his position untenable, and to have him replaced by somebody more congenial to the leaker,” he told BBC Radio 4’s Today programme.

In the memos, obtained by The Mail On Sunday, Sir Kim suggested that in order to communicate with the president “you need to make your points simple, even blunt”.

In a scathing assessment of the White House, he 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.”