Boris Johnson is under fire from colleagues and opponents after Sir Kim Darroch resigned as the UK's ambassador to the US, following a public row with Donald Trump.

Darroch reportedly decided to resign after watching Johnson refusing to back him to remain in his post.

Johnson's colleagues accused the frontrunenr to be prime minister of throwing Darroch "under the bus."

The opposition Labour party brand him a "Donald Trump patsy."

The row came after confidential memos he sent about president Donald Trump were leaked to the press, labeling Trump's administration as "uniquely dysfunctional" and "inept"

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LONDON — Boris Johnson has been branded "contemptible" by his colleagues and a "Donald Trump patsy" by his opponents, after reports suggested his refusal to back Sir Kim Darroch forced the United Kingdom's ambassador to the United States to resign.

Darroch was forced out on Wednesday saying that it was "impossible" for him to remain in post after a public row with the US President.

The UK's ambassador to the US resigned after confidential memos he wrote labeling Trump's administration "dysfunctional" and "incompetent" were leaked to the press over the weekend.

Johnson on Tuesday refused to say he should remain in post, after the US president tweeted a series of attacks on Darroch as "pompous," and "stupid" and declared that the White House would no longer work with him.

Speaking during a televised leadership debate on ITV, Johnson also refused to criticise Trump for publicly insulting prime minister Theresa May, saying only that the president had been "dragged into a British political debate."

A senior ally of Mr Johnson told the Times: "We don't want to put the whole special relationship on the edge because of a row about one person. We do not have anything to gain from a running spat with the White House."

Johnson's refusal to back Darroch, was key to his decision to step down, the BBC reported.

Darroch's departure triggered outrage among colleagues, some of whom are backing Johnson's rival foreign secretary Jeremy Hunt to replace May as Conservative leader and prime minister.

Foreign Office minister Sir Alan Duncan accused Johnson of having "basically thrown our top diplomat under a bus."

He said that Johnson's refusal to defend Darroch was "pretty contemptible," adding that: "There are a lot of people here in the Commons who are very, very angry and feel he has lost so much respect for having done what he's done."

Conservative MP Sir Patrick McLoughlin agreed, saying: "It is unedifying to see someone who wants to be Prime Minister failing to stand up for hard working civil servants, who have done nothing wrong, under attack from foreign governments.

"Leadership involves standing up for your team. If we don't call out those who want a witch-hunt through the civil service we are complicit in creating divisions that may never heal."

The opposition Labour party also rounded on Johnson, accusing him of failing to stand up for the UK.

"Johnson is effectively behaving as a Donald Trump patsy," a spokesperson for Labour leader Jeremy Corbyn said on Wednesday.

"He won't stand up to Donald Trump and be won't stand up for Britain."

A spokesperson for May on Wednesday said that "an appointment will be made in due course" for Darroch's successor.