The leaker of a diplomatic memo about Donald Trump could face a police probe, a minister confirmed.
The frank memos from Sir Kim Darroch, the ambassador to Washington, were leaked to a Sunday newspaper.
He described the White House as "dysfunctional" and "inept" in a scathing assessment of Mr Trump.
The extraordinary breach of confidentiality triggered a political firestorm on both sides of the Atlantic as Mr Trump made clear his anger at Sir Kim.
Responding to an urgent question on the leak, Foreign Office Minister Sir Alan Duncan told MPs that "If evidence of criminality is found then yes the police could be involved.
He added: "The focus is to establish who is responsible for this despicable leak."
It echoes words from Number10 earlier.
Theresa May's spokesman said if “any evidence of criminality” is found during the course of the Cabinet Office inquiry then the police will be involved.
Asked if Mrs May agreed with the contents of Sir Kim's leaked assessment of the Trump administration, the spokesman said: "The PM does not agree with that assessment."
He added: "The Prime Minister has a good relationship with the president and the Government works closely and constructively with the administration across a wide range of issues."
The spokesman said there was "nothing to suggest" hostile state actors had been involved in the leak.
In the cache of documents, Sir Kim gives a scathing assessment of the White House: "We don't really believe this administration is going to become substantially more normal; less dysfunctional; less unpredictable; less faction riven; less diplomatically clumsy and inept."
He questioned whether the White House "will ever look competent".
In one of the most recent documents, Sir Kim refers to "incoherent, chaotic" US policy on Iran and questions Mr Trump's publicly stated reason for calling off a retaliatory air strike against Tehran following the downing of an American drone.
The US and Iran have been at the brink of armed conflict over tensions in the Gulf and Mr Trump stated he called off a planned air strike with minutes to spare because of the potentially high number of casualties.
But Sir Kim said the explanation "doesn't stand up" and suggested it may have been motivated by Mr Trump's focus on the 2020 re-election campaign and his previous promises not to involve the US in foreign conflicts.
"It's more likely that he was never fully on board and that he was worried about how this apparent reversal of his 2016 campaign promises would look come 2020," Sir Kim said.
He said it was "unlikely that US policy on Iran is going to become more coherent any time soon" as "this is a divided administration".
