LONDON - British police are seeking an "unprecedented" court order to force the newspaper that led the coverage of a phone-hacking scandal engulfing Rupert Murdoch's News Corp empire to reveal its sources, the paper said on Friday.In a story on its website, the left-leaning Guardian said London's Metropolitan Police (MPS) was trying to use the Official Secrets Act to force two of its reporters to disclose their confidential sources. The act is designed to protect classified information and is usually applied to matters of national security and espionage.The Guardian newspaper's reports have helped keep the story at the top of the political agenda in Britain and played a part in forcing News Corp to close the 168-year-old News of the World tabloid at the centre of the scandal.The story has pulled in Murdoch's son James, forced News Corp to withdraw a bid to buy the part of pay TV group BSkyB it did not already own and shaken the British political establishment.Britain's most senior police officer and the top counter-terrorism officer also quit amid a growing furore.The Guardian said the police wanted to use the act to find the source of information that led to the revelation in July that murdered schoolgirl Milly Dowler's phone had been hacked.The disclosure caused a wave of public anger which ultimately brought about the downfall of the News of the World, and led to the resignation of Rebekah Brooks, chief executive of News International, the British newspaper arm of News Corp."We shall resist this extraordinary demand to the utmost," the Guardian's editor Alan Rusbridger said in the online report.Detectives are investigating the phone-hacking allegations and have already arrested 16 people including Brooks and Andy Coulson, the former editor of the News of the World who went on to work as Prime Minister David Cameron's media chief.One of the detectives involved in the investigation was also arrested and suspended last month on suspicion of leaking details about the case.The paper was the first to report a number of the high-profile arrests in the phone-hacking inquiry. One of the Guardian's reporters was quizzed by police investigating the leaks.The MPS said it was seeking a "production order" against the Guardian and one of its reporters over potential breaches of the Official Secrets Act. The paper said the application would be heard at a London court on Sept 23."Operation Weeting (the phone-hacking inquiry) 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," the police said in a statement.The force added that it paid tribute to "the Guardian's unwavering determination to expose the hacking scandal and their challenge around the initial police response" and was not trying to prevent investigative journalism.Mark Lewis, lawyer for the Dowler family, told BBC television it was "Alice in Wonderland justice".In a Reuters interview, leading human rights lawyer Geoffrey Robertson criticized the way the police had conducted their inquiry into the phone-hacking scandal, accepting the News of the World's initial defense that it was the work of a lone reporter."I think the police have acted extremely stupidly in the course of this whole matter from the time they allowed only one journalist to be prosecuted and this is another example," he said in an interview with former Sunday Times editor Harold Evans who now works for Reuters as editor-at-large."Using the official secrets act to obtain a journalist's source is really something of an outrage," Robertson added."Police maybe think they can take these liberties against good journalists because there are so many bad ones out there."