Scotland Yard was on Saturday accused of trying to muzzle press freedom after it invoked the Official Secrets Act, normally used to prevent espionage, to force The Guardian to disclose its confidential sources about the News of the World phone-hacking scandal.

At the heart of the unprecedented police move is a Guardian report which revealed that the NoW went to the extent of hacking the phone of a murdered schoolgirl, Milly Dowler, in search of stories.

The report provoked national outrage forcing Rupert Murdoch to close down the 160-year-old tabloid. It also led to a wave of high-profile resignations at Mr. Murdoch's media group News International, including its chief executive and former NoW Editor Rebekah Brooks.

The Metropolitan Police, claiming that the report was based on an unauthorised leak, applied for a court order against The Guardian “in order to seek evidence of offences connected to potential breaches relating to Misconduct in Public Office and the Official Secrets Act”.

“The application is about the MPS seeking to identify evidence of potential offences resulting from unauthorised leaking of information,” it said in a statement defending its action.

The Guardian called it “an unprecedented legal attack on journalists' sources” and its Editor Alan Rusbridger, condemning the move as “vindictive”, said: “We shall resist this extraordinary demand to the utmost”.

The move was also condemned by MPs, rights groups and the National Union of Journalists which described it as a “very serious threat to journalists” arguing that protection of sources was “an essential principle… repeatedly reaffirmed by the European court of human rights as the cornerstone of press freedom.”

“Journalists have investigated the hacking story and told the truth to the public. They should be congratulated rather than being hounded and criminalised by the state… The NUJ shall defend it. In 2007 a judge made it clear that journalists and their sources are protected under article 10 of the Human Rights Act and it applies to leaked material. The use of the Official Secrets Act is a disgraceful attempt to get round this existing judgment,” said NUJ general secretary, Michelle Stanistreet.

More In: International | News