There is no evidence the publication of the email in which Sir Kim Darroch criticised President Trump’s administration was due to a hack, a Foreign Office minister has said.
Sir Kim stepped down as ambassador to the US on Wednesday, saying it was “impossible” for him to continue.
Sir Alan Duncan told the Commons he had not ruled out a hack – but said there was currently no evidence of one.
He added Sir Kim still had something to offer and could be given a new role.
“We do not, at the moment, have any evidence that this was a hack so our focus is on finding someone within the system who has released illicitly these communications,” Sir Alan said.
Prior to Sir Kim’s resignation, President Trump said that the US would no longer deal with Sir Kim.
The US president had branded him “a very stupid guy” after confidential emails emerged where the ambassador had called his administration “clumsy and inept”.
Sir Alan also failed to rule out Prime Minister Theresa May appointing a new US ambassador before she leaves office on 23 July.
Shadow foreign office minister Liz McInnes had asked if the Foreign Office would ensure a new ambassador to the US was appointed before the new prime minister takes office “so we still have at least one UK representative willing to speak truth to power in Washington”.
Answering her question, Sir Alan said: “The next ambassador will be appointed in the usual way by the prime minister on the foreign secretary’s recommendation, with the approval of Her Majesty The Queen.”
Sir Alan added Sir Kim “quite rightly” received the full support of Mrs May and the “entire Cabinet” prior to his resignation – and that the government “profoundly regrets” the ambassador’s decision to step down.
“It is an outrage that a selection of his very professional reports back to London should have been leaked,” Sir Alan continued.
“In an act of selfless duty, Sir Kim made the decision to resign in order to relieve the pressure on his family and colleagues and to protect the UK-US relationship.”
Sir Kim’s resignation prompted widespread support for him – as well as criticism of Tory frontrunner Boris Johnson.
According to some Whitehall sources, Sir Kim decided to resign after Mr Johnson refused to support him during the Tory leadership debate on Tuesday night, said BBC diplomatic correspondent James Landale.
Mr Johnson was asked repeatedly by fellow leadership candidate Jeremy Hunt whether he would keep Sir Kim in post if he became prime minister, but refused to answer.
Following Sir Kim’s resignation, Mr Johnson said he was “a superb diplomat” and whoever was responsible for the leak “has done a grave disservice to our civil servants”.
Asked why he was not more supportive of Sir Kim, he said it was “wrong to drag civil servants into the political arena”.