UK police are seeking a court order to make the Guardian newspaper disclose their confidential sources that sparked the phone-hacking scandal centered around Rupert Murdoch's media empire in the country.

The British daily Guardian's revelation in July that police had never properly pursued the News of the World for hacking the phone of a missing murdered girl caused a wave of public revulsion worldwide.

In an unprecedented legal attack on journalists' sources, Scotland Yard officers claim the Official Secrets Act, which has special powers usually aimed at espionage, could have been breached when two of the Guardian reporters revealed that the phone of Milly Dowler, who was later found murdered, had been hacked,the daily said.

Now the police are demanding source of information be handed over.

Guardian editor Alan Rusbridger promised to "resist this extraordinary demand to the utmost".

Tom Watson, the former Labour minister who has been prominent in exposing hacking by the News of the World, said: "It is an outrageous abuse and completely unacceptable that, having failed to investigate serious wrongdoing at the News of the World for more than a decade, the police should now be trying to move against the Guardian. It was the Guardian who first exposed this scandal."

The NUJ general secretary, Michelle Stanistreet, said that this is a very serious "threat" to journalists and the NUJ will fight off this vicious attempt to use the Official Secrets Act.

"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 general secretary, Michelle Stanistreet, said:

The uproar over police inadequacy in the phone hacking scandal led to the resignation of the top officers at Scotland Yard. It also brought about the closure of the News of the World itself.