Downing Street has reiterated the UK's ambassador to the US has Theresa May's "full support", despite Donald Trump saying he will no longer work with him.
The US president was responding after leaked emails revealed Sir Kim Darroch had called his administration inept.
In a series of tweets, Mr Trump also criticised Mrs May's handling of Brexit saying she had created "a mess".
Number 10 called the leak "unfortunate" and said the UK and US still shared a "special and enduring" relationship.
A Downing Street spokesman said: "We have made clear to the US how unfortunate this leak is. The selective extracts leaked do not reflect the closeness of, and the esteem in which we hold, the relationship.
But he said ambassadors needed to be able to provide honest assessments of the politics in their country, and the prime minister stood by Sir Kim.
"The UK has a special and enduring relationship with the US based on our long history and commitment to shared values and that will continue to be the case," he said.
Speaking on Monday following Mr Trump's initial comments on the leaked emails, Downing Street said the prime minister did not agree with Sir Kim's assessment but had "full faith" in him.
Police were urged to open a criminal investigation into the leak in addition to an internal inquiry launched by the government.
Tom Tugendhat, chairman of the foreign affairs committee, told MPs he had made the request in a letter to the Met Police.
The Met said it had received Mr Tugendhat's request but had not received an official governmental referral of allegations in relation to the Official Secrets Act.
Such a referral would be required for a criminal investigation to be considered, a Met spokesman said.
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