"Since the leak of legitimate paperwork from this Embassy there was a vast deal of hypothesis surrounding my enviornment and the duration of my closing term as ambassador", he wrote.
In his statement he revealed that he wanted to "put an end" to the speculation around his future following the furore over the leaking of the damaging secret memos.
The diplomat said "the current situation makes it impossible for me to carry out my role" following the leak of unflattering remarks made about US President Donald Trump. Parliament that she had spoken with Darroch Wednesday morning, and his resignation was a subject of "deep remorse".
May said she regretted that Darroch felt the need to resign, adding that officials needed to be able to give "full and frank advice".
Boris Johnson, expected to become the new prime minister, said nothing in Darroch's support.
The Prime Minister's spokesman said Mr Darroch would continue in his post until his successor is appointed, but did not offer any timescale, saying only that a new ambassador would be named "in due course".
Asked why he was not more supportive of Sir Kim, he said it was "wrong to drag civil servants into the political arena".
The Independent says Mr Johnson is facing a backlash from within the Conservative Party after Sir Kim resigned as U.S. ambassador.
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The i says the resignation of Sir Kim sent shockwaves through the Government and unleashed "fury in the civil service". "I'm not going to quote from our reports home, but there may be some similarities".
Emily Thornberry, the spokeswoman on foreign affairs for the main opposition Labour Party, said Darroch "has been bullied out of his job, because of Donald Trump's tantrums and Boris Johnson's pathetic lick-spittle response".
"The wacky Ambassador that the U.K. foisted upon the United States is not someone we are thrilled with, a very stupid guy", the President wrote.
"Boris Johnson has basically thrown our ambassador under a bus", Mr. Duncan said Wednesday.
Like his predecessors, Darroch was a prominent figure in Washington, meeting frequently with high-level US officials and hosting parties at the stately British Embassy. Sir Simon McDonald told Darroch he was "the target of a malicious leak" and that despite the scandal, "You demonstrate the essence of the values of British public service".
Johnson is the strong favorite to win a Conservative leadership contest and succeed May as party leader and prime minister. "I don't think it affects the bilateral relationship too much", he said, predicting the next prime minister will start with a clean slate, select "one of their very good diplomats" as the next ambassador, and "I assume be touted as a great success".
Trump has previously suggested the job go to Nigel Farage, a British eurosceptic politician who now leads the Brexit Party and who, like Johnson, was a prominent voice in the 2016 referendum campaign for Brexit.