Memos from Kim Darroch describing the Trump administration as inept were leaked to a British newspaper, infuriating the United States president, who launched a Twitter attack on both the envoy and outgoing prime minister Theresa May, who had given Darroch her full support.
Prime Minister Theresa May said Wednesday it was a "matter of regret" that Darroch resigned.
"I am extremely angry that a good man has been brought down by a bad leak of highly classified documents and by a president as vindictive and spiteful as Kim Darroch said he was in his highly classified communications".
He also said he would no longer work with Kim Darroch. "The whole cabinet rightly gave its full support to Sir Kim on Tuesday".
Speaking on the BBC's Newsnight programme, Mr Raab, who is backing Mr Johnson in the Conservative leadership contest, labelled Sir Kim's comments as "wrong" and claimed diplomatic cables should not include personalised remarks.
"It's a problem, but I don't know that it has a chilling effect over time because in the end people have jobs to do and they do their jobs", said Ronald Neumann, a retired three-time US ambassador who is the president of the American Academy of Diplomacy. "Boris Johnson's failure last night to stand up for him - and stand up to the behaviour of Donald Trump - spoke volumes".
"Somebody has, for whatever malicious reasons, sought to either damage the UK-US relationship or indeed Sir Kim personally", he told reporters.
Speaking after Darroch's resignation, Johnson said he hoped whoever had leaked the cables "is run down, caught and eviscerated".
Trump, who subsequently launched a series of derisive tweets, disinviting the United Kingdom ambassador from White House functions and cutting off staff interaction with him, has stayed silent since news of Sir Kim Darroch's resignation and the major USA media websites are also not reporting the story.
"Boris Johnson has basically thrown our ambassador under a bus", Mr. Duncan said Wednesday.
The leak of this confidential cable and May's assertion that her envoy was perfectly within his right making such a frank assessement has prompted Trump to call Sir Kim a very stupid guy with whom he will have nothing more to do.
"Deeply saddened to hear of the resignation of Sir Kim Darroch", Hunt posted in a tweet. Jonathan Powell, former prime minister Tony Blair's chief of staff, told Britain's Channel 4 News that the attempt to force Darroch from office followed similar efforts to punish career British officials suspected of insufficient enthusiasm for Brexit, according to The Intercept website.
It's unusual, but not unknown, for non-diplomats to become ambassadors, and some have suggested Johnson as prime minister might appoint someone seen as strongly pro-Brexit and friendly to Trump.
His boss in the UK Foreign Office replied saying he was accepting the resignation with regret, adding "you are the best of us".
Some U.K. officials are alleging the leak could have been staged to sow discord between Britain and the U.S.
It led to a scathing tirade from the USA president. This has brought home to me the depth of friendship and close ties between our two countries.