THE inquiry into the leak of diplomatic cables criticising Donald Trump’s White House is focusing on whether “someone within the system” was responsible, a Foreign Office minister has said.

Sir Alan Duncan said there was no evidence the dispatches from Sir Kim Darroch – the UK’s ambassador to the US – had been obtained through computer hacking.

Instead, he said the investigation was looking at the possibility they had been “illicitly” released by someone with access to diplomatic reports.

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Darroch announced this week he was standing down from his posting in Washington, saying his position had become “impossible” after a barrage of abuse from Trump.

Downing Street has said “initial discussions” have taken place with the police who could become formally involved in the leak inquiry if there was evidence of “criminal activity”.

In the Commons yesterday, Duncan told MPs: “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 ... that is where the inquiry is primarily focused at the moment.”

There was continuing anger among many MPs at the role played by former foreign secretary Boris Johnson, whose repeated refusal to back Darroch in Tuesday’s Tory leadership television debate was widely seen to have contributed to his decision to quit.

The frontrunner to succeed Theresa May insisted it was nothing to do with him, saying he was “very surprised” at the construction which had been placed on events.

“I can’t believe they’re trying to blame me for this,” he told The Sun.

“It seems bizarre to me. I’m a great supporter of Kim’s. I worked very well with him for years. I think that he’s done a superb job.”

Duncan, who previously accused Johnson of having thrown Darroch “under a bus”, said he hoped the the “entire apparatus of government” would ensure the ambassador was looked after following his departure from Washington.

“Sir Kim Darroch’s career is not over. I hope the House will appreciate that although this is a difficult moment, it doesn’t mean that’s the end of his career,” he told MPs.

“I hope the Foreign Office and the entire apparatus of government will look after him, appreciate his merits and make sure he can be redeployed somewhere else for the benefit of our United Kingdom.”

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Meanwhile, Downing Street has refused to be drawn on whether May intends to appoint a new ambassador before she leaves office in two weeks’ time.

If May were to make the appointment it would deny Johnson the chance to put his choice of envoy in place if he became PM. It would also give his leadership rival Jeremy Hunt a role in selecting the new ambassador. As Foreign Secretary, Hunt advises the prime minster on such appointments.

Allies of Johnson have insisted it must be for the next prime minister to decide who Britain’s new envoy to the US should be. One told The Times: “With two weeks to go before the new prime minister takes over it would seem odd if [the PM] plunged in and appointed someone. It’s such an important decision you would think it would be made by the new prime minister.”

Duncan hinted an early appointment may be unlikely. “We do really want to make sure we get the very best person and I think it’d be a pity if in the interests of alacrity we chose a number two rather than a number one,” he said. “So it’s not for me to make any further comment on that really. I don’t know whose names might be in the frame, but that’s a matter for the prime minister to decide.”

May’s spokesman said the appointment would be made “in due course”.