Donald Trump’s White House is “uniquely dysfunctional” and “inept”, according to a cache of scathing leaked memos from the UK’s ambassador in Washington.

The UK government is investigating who leaked the sensitive documents which detail Sir Kim Darroch’s assessments of the Trump administration from 2017 to the present – and could prove highly embarrassing for Britain’s Foreign Office.

Officials insisted the relationship with the White House could withstand the “mischievous behaviour” of the leak and defended Sir Kim’s candid style.

The diplomatic memos, obtained by the Mail on Sunday, suggest that in order to communicate with the President “you need to make your points simple, even blunt”.

Sir Kim gives a scathing assessment of the White House: “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.”

He questioned whether the White House “will ever look competent”.

Outspoken eurosceptic and Trump supporter Nigel Farage called for Darroch to be sacked.

“Kim Darroch is totally unsuitable for the job and the sooner he is gone the better,” Mr Farage tweeted.

He told the newspaper that Sir Kim was “the wrong person to be the British ambassador” under a Trump administration because he is “globalist in outlook, totally opposed to the Trump doctrine”.

Ambassador Kim Darroch also said the US president radiated “insecurity”. Photo: Getty

Dominic Raab, a leading eurosceptic in Prime Minister Theresa May’s Conservatives and a former Brexit secretary, also criticised Sir Kim for giving “very personalised judgement” in the memos.

Mr Raab told Sky New some of the comments “may in retrospect be regarded as unwise”.

“But at the end of the day I am sure the two sides will get beyond any of those kind of comments,” he said.

Following Mr Trump’s state visit to the UK in June, Sir Kim warned that although the President had been “dazzled” by the pomp and ceremony of the trip, his administration would remain self-interested and “this is still the land of America First”.

Sir Kim refers to “incoherent, chaotic” US policy on Iran and questions Mr Trump’s publicly stated reason for calling off a retaliatory air strike against Tehran following the downing of an American drone.

The US and Iran have been at the brink of armed conflict over tensions in the Gulf, and Mr Trump stated that he called off a planned air strike with minutes to spare because of the potentially high number of casualties.

But Sir Kim said that the explanation “doesn’t stand up”, and suggested it may have been motivated by President Trump’s focus on the 2020 re-election campaign and his previous promises not to involve the US in foreign conflicts.

“It’s more likely that he was never fully on board and that he was worried about how this apparent reversal of his 2016 campaign promises would look come 2020,” Sir Kim said.

He said it was “unlikely that US policy on Iran is going to become more coherent any time soon” as “this is a divided administration”.

In a particularly sensitive leak, a 2017 letter to the National Security Adviser Sir Mark Sedwill – sent 150 days into the Trump administration – laid bare the trouble in the White House.

Media reports of “vicious infighting and chaos” were “mostly true” despite the President’s attempts to brush them off.

Referring to the early allegations of collusion between the Trump campaign and Russia, the memo said “the worst cannot be ruled out”.

A Foreign Office spokesman said: “The British public would expect our ambassadors to provide ministers with an honest, unvarnished assessment of the politics in their country.

“Their views are not necessarily the views of ministers or indeed the government.

“But we pay them to be candid. Just as the US ambassador here will send back his reading of Westminster politics and personalities.

“Our team in Washington have strong relations with the White House and no doubt … these will withstand such mischievous behaviour.”

-AAP