Theresa May and her most senior officials were dragged into a row over press freedom last night.

The row emerged after the Cabinet Office called in Neil Basu, the head of the Metropolitan Police specialist operations.

Neil Basu is the senior police officer who has threatened to prosecute anybody who publishes leaked diplomatic cables.

He appears to have set out to 'protect the Government from embarrassment' after he issued a warning that the publication of the leaked memos could in itself be 'a criminal matter.'

Mr Basu said he had concluded that the leaks had 'damaged the UK's international relations with the US.'

But a leading QC suggested they simply caused 'embarrassment' to the Government and accused the police of a 'politically motivated witch hunt' against publishers.

His warning prompted a sharp response from Jeremy Hunt, Boris Johnson, and Matt Hancock, the Health Secretary, along with calls for him to resign if he refused to drop the threat.

Mr Johnson said pursuing media outlets for bringing the information into the public domain would have a 'chilling effect on public debate,' while Mr Hancock, a former culture secretary, warned: 'The state threatening media freedom is a dangerous road to tread.'