British police say they have opened an investigation into a leak of confidential memos that led to the resignation of the UK's ambassador to Washington.
Kim Darroch quit on Wednesday after Donald Trump called him "stupid" and "wacky" following the publication of the confidential memos by a newspaper. In them, Darroch called Trump's administration inept.
London's Metropolitan Police said on Friday its counter-terrorism command, which takes national responsibility for investigating allegations of criminal breaches of the Official Secrets Act, was leading the investigation.
"Given the widely reported consequences of that leak I am satisfied that there has been damage caused to UK international relations, and there would be clear public interest in bringing the person or people responsible to justice," Met Assistant Commissioner Neil Basu said in a statement.
A file photo of former British Ambassador Sir Kim Darroch at the British Embassy in Washington Source: AAP
"I would say to the person or people who did this, the impact of what you have done is obvious. However, you are now also responsible for diverting busy detectives from undertaking their core mission. You can stop this now. Turn yourself in at the earliest opportunity, explain yourself and face the consequences."
It comes as Boris Johnson, front runner to be Britain's next prime minister, denied he was responsible for the resignation of Darroch but admitted his comments had been a factor in the shock departure of one of the country's most senior diplomats.
The former London mayor has been heavily criticised by MPs in his own party and the opposition for failing to defend Darroch after Trump attacked the envoy for leaked remarks describing the US administration as inept.
Darroch resigned after days of scathing criticism from the US president on Twitter. A diplomatic source told Reuters that the lack of support from Johnson during a televised debate with his rival for the premiership, foreign minister Jeremy Hunt, had also been a factor.
Johnson said Darroch had not watched the debate but had heard an inaccurate account of what was said. He said he had not defended the ambassador more because he did not think civil servants should be dragged into political disputes.
"(Darroch) said that what somebody had relayed to him had certainly been a factor in his resignation," he told BBC television in a testy interview. "I think unfortunately what I said on that TV debate was misrepresented to Kim."
Johnson pointedly refused to back Darroch during the televised debate on Tuesday, leading to accusations from fellow Conservative Party MPs that he had thrown the ambassador "under the bus" in order to bolster his own ties with Trump.
At one point he also goaded Hunt, asking how long he would keep Darroch in place after vowing to retain him.
Boris Johnson (L) refused to back British ambassador Kim Darroch (R) during a televised debate. (AAP) Source: AAP
Asked in Friday's interview if he would be "as craven" a prime minister as he has been a candidate, Johnson said: "We have been very forthright with the United States of America and I will continue to be forthright."
Johnson and Hunt are locked in a battle to succeed Theresa May, who resigned as prime minister after failing three times to get parliamentary approval for a withdrawal deal for Britain's exit from the European Union.
The new prime minister will be named on July 23 and take office the following day.
