Phone hacking: Met seeking Milly sources, says Guardian
Scotland Yard is trying to force the Guardian to reveal the sources behind its story about the phone hacking of murdered schoolgirl Milly Dowler.
July's report reignited the News of the World phone-hacking scandal, leading to the tabloid's closure.
The Met Police said it was probing potential Official Secrets Act breaches and misconduct and not trying to stop investigative journalism.
It confirmed it had applied for a production order against the Guardian and one of its reporters.
The Metropolitan Police's Operation Weeting is investigating claims of phone hacking at the News of the World.
The force is claiming that the Official Secrets Act could have been breached in relation to the original article on the hacking of Milly Dowler's mobile phone voicemail, the Guardian reported on Friday.
The paper added that police were due to go to the Old Bailey in London on 23 September, in an attempt to force the handover of documents relating to sources for a number of articles.
The Guardian says section 5 of the 1989 Official Secrets Act allows prosecutions for passing on "damaging" information leaked to them by government officials in breach of section 4 of the same act, including police information "likely to impede … the prosecution of suspected offenders".
According to the paper, there has been only one previous attempt to use the act against a journalist, in a case which collapsed in 2000.
BBC home affairs correspondent Tom Symonds said: "It's highly unusual for the Official Secrets Act to be used in this way; the act prohibits the disclosure of material that may impede the detection of crime."
Media commentator Steve Hewlett, whose work appears in the Guardian, told the BBC the police application appeared to be "heavy handed" and there had been no suggestion that officers were being paid for any information that may have appeared in the newspaper.
Guardian editor Alan Rusbridger said: "We shall resist this extraordinary demand to the utmost."
The court application by the Met comes after Guardian reporter Amelia Hill was questioned under caution earlier this month over alleged police leaks surrounding the hacking inquiry. In August, a Met Police detective constable who worked in the Operation Weeting team was arrested over the unauthorised disclosure of information.
Another 16 people have been arrested on suspicion of phone hacking - 15 of whom are still under investigation - since Operation Weeting was launched in January.
Former News International chief executive Rebekah Brooks and ex-Downing Street communications chief Andy Coulson are among those questioned by police.
The scandal has led Met Police Commissioner Sir Paul Stephenson and Assistant Commissioner John Yates to resign, and the News of the World to close down after 168 years.
In a statement, the Met Police said: "The application is about the MPS [Metropolitan Police Service] seeking to identify evidence of potential offences resulting from unauthorised leaking of information.
"Operation Weeting is one of the MPS's most high profile and sensitive investigations so of course we should take concerns of leaks seriously to ensure that public interest is protected by ensuring there is no further potential compromise."
It added: "We pay tribute to the Guardian's unwavering determination to expose the hacking scandal and their challenge around the initial police response.
"We also recognise the important public interest of whistle blowing and investigative reporting, however neither is apparent in this case."