Scotland Yard was criticized for having warned media organizations not to leak leaked government documents.
Neil Basu, deputy commissioner of the Metropolitan Police, advised the editors that it could be "a criminal matter".
His comments came when a criminal investigation into the leak of diplomatic emails by British Ambassador to the United States, Sir Kim Darroch, was launched.
The Evening Standard editor, George Osborne, described Basu's statement as "stupid" and "ill-advised".
The investigation was initiated by the Met Police Counter Terrorism Command, which has national responsibility for investigating allegations of violations of the Official Secrets Act.
"The publication of leaked communications in the knowledge of the damage they have caused or are likely to cause can also be a criminal matter," Basu said.
He added, "I would advise all owners, publishers and publishers of social and mainstream media not to republish the leaked government documents that may already be in their possession or offered to them and return them to the police or hand them over her rightful owner, Her Majesty's Government. "
Mr Osborne, former Chancellor of the Exchequer tweeted in order to maintain credibility, Commissioner Cressida Dick was told by" this very stupid and ill-advised statement by a junior officer, the does not seem to understand much about press freedom. "
Other newspaper editors and MPs also criticized Mr. Basu's statement.
The Sunday Times political editor, Tim Shipman, asked if Ms. Dick had threatened the "grim, absurd, anti-democratic statement … Journalists arrested for printing governmental leaks?"
He added on Twitter: "Do you have an understanding of a free society? This is not Russia."
Peter Spiegel, senior editor of the Financial Times in the US, wrote : What will you do, Met Police, to arrest us?
Foreign Minister Jeremy Hunt said he defended the right of the press to publish leaks if they judge it to be in the public interest ".
His rival in the Tory leadership, Boris Johnson, said it was right that the person that was responsible for the leak, was "hunted and persecuted", but it was wrong for the police to target the media.
He said: "An indictment on this basis would constitute a violation of press freedom and a deterrent to publication."
MP Tom Tugenhadt, chair of the Foreign Affairs Committee, told the Today program from Radio 4, saying it was "a reasonable request" to urge the media not to release leaked documents jeopardizing security, but he "doubted" if it was a crime.
Former Secretary of Defense Sir Michael Fallon, however, said the leak was a clear violation of the Official Secrets Act and the police were entitled to prevent further disclosure.
"If they are [the press] If they receive stolen material, they should return it to their rightful owner," he told the Today program.
"You should also be aware of the great damage that has already been done and the potentially even greater harm that others have been wreaking havoc with the Official Secrets Act."
The government already has an internal investigation into publication the memos that were critical of the Trump administration – and sparked a furious reaction from the US president who said no longer to negotiate with Sir Kim.
President Trump described him as "a very stupid guy," after confidential emails appeared in which the ambassador described his administration as "awkward and incompetent."
Sir Kim resigned as Ambassador on Wednesday, saying it was "impossible" for him to continue.
Sir Kim's resignation sparked broad support for him – and criticism of Tory leader Johnson.
According to some sources in Whitehall, Sir Kim decided to resign after Mr. Johnson had not fully supported him in a televised debate on Tuesday night.
Mr. Johnson denied any guilt and said he had spoken to him Sir Kim said Thursday he had not followed the ITV debate to express his grief over his resignation, and the ambassador told him. However, on Friday, Mr. Johnson told the BBC a "misrepresentation" of his remarks relayed to Si. Kim was "a factor" in his decision to resign.
Prime Minister Theresa May Sir Kim's departure was "a matter of regret" and officials should be able to "provide comprehensive and open advice" To give.
Shadow Foreign Minister Liz McInnes said Sir Kim Darroch is "just doing his job" and the criminal investigation is "welcome".