Scotland Yard has launched a criminal investigation into the leak of classified diplomatic emails sent by Britain’s ambassador to the US which were critical of the Donald Trump administration.

Sir Kim Darroch has since been forced to resign from his post after his views of an “inept” and "dysfunctional" Trump government hit the newspapers earlier this month and attracted direct social media attacks from the US President.

“The Metropolitan Police Counter Terrorism Command, who take national responsibility for investigating allegations of criminal breaches of the Official Secrets Act, has launched a criminal investigation,” Neil Basu, the Met Police’s counter-terrorism lead, said in a statement.

“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. The investigation will be reviewed at every stage to ensure a proportionate investigation is undertaken,” he said.

However, the Met Police Assistant Commissioner, one of the UK’s senior-most police officers, also issued a warning about the further publication of leaked material.

He said: “The publication of leaked communications, knowing the damage they have caused or are likely to cause may also be a criminal matter.

“I would advise all owners, editors and publishers of social and mainstream media not to publish leaked government documents that may already be in their possession, or which may be offered to them, and to turn them over to the police or give them back to their rightful owner, Her Majesty’s Government.”

This aspect of the police intervention has attracted strong criticism, with some UK media chiefs describing it as “ill-advised” and an attack on media freedom. As the criticism mounted, the Met Police Assistant Commissioner was forced to issue a follow up statement.

Basu said: “The Metropolitan Police respects the rights of the media and has no intention of seeking to prevent editors from publishing stories in the public interest in a liberal democracy. The media hold an important role in scrutinising the actions of the state.

“However, we have also been told the publication of these specific documents, now knowing they may be a breach of the Official Secrets Act, could also constitute a criminal offence and one that carries no public interest defence… We have a duty to prevent as well as detect crime and the previous statement was intended to alert to the risk of breaching the OSA.”

Both candidates currently contesting a leadership race to replace Theresa May as British Prime Minister spoke out against this perceived warning to the media.

Boris Johnson said he condemned the “chilling effect on public debate”, while Jeremy Hunt said: “I defend to the hilt the right of the press to publish those leaks”.

David Davis, a former UK Brexit secretary, was more critical and called for Neil Basu to be stripped of his role in the investigation and replaced by an officer who puts a free press before “the state's reputation”.

The diplomatic row has played out for weeks since the publication of the leaked emails dating back to 2017, which were extremely critical of the Trump administration. It led to an open war between the White House and the UK government as Trump took to Twitter to brand Darroch a “very stupid man” and widened his attacks to Theresa May.

In an apparent backtrack last week, the US President said he wished the British ambassador well and that he had been told Darroch had actually said "some very good things" about him.