Journalists have warned that the arrest of a reporter in a series of police raids as part of a probe into leaks sets a worrying precedent for UK press freedom.
And Sunday Times Northern Ireland editor Liam Clarke, whose home was raided by police four years ago, said increasing police powers mean journalists may have to "take precautions normally associated with organised crime" to maintain confidentiality.
Police raided a journalist's home and the offices of the Milton Keynes Citizen and the MK News using a warrant obtained from a magistrate under the Police and Criminal Evidence Act (PACE).
The raids are part of an ongoing joint investigation by Thames Valley Police and Hertfordshire Police into police leaks of "sensitive information" to local media.
Milton Keynes Citizen reporter Sally Murrer was arrested last Tuesday on suspicion of aiding and abetting misconduct in public office.
She was released on police bail after spending Tuesday night in the cells at Banbury Police Station while her home was searched. Police took several of her notepads and a computer from the Citizen's Bletchley office.
Two police officers, one from Hertfordshire and one from Thames Valley, a soldier and a 52-year-old man from Hertfordshire, who is not thought to be a journalist, were also arrested in connection with the case. Those arrested have had their bail extended to 19 June.
Johnston Press, owner of the Citizen, released a statement supporting Murrer and said it would offer independent legal advice. The company said it had "no reason to suppose its reporter was not carrying out journalistic responsibilities fairly and legally".
The Citizen's rival paper, MK News, was raided under a PACE warrant on Wednesday. Police took two notebooks from a reporter but there were no arrests.
Steve Lowe, group editor of LSN Media, MK News's parent company, said the paper had received two leaked stories from a Thames Valley Police officer. One was about how officers at a Milton Keynes police station lost a set of keys to their cells.
He said: "There was a police officer and he had leaked us a story – that's absolutely true. I can see it's embarrassing, but we had a visit from the police without warning.
"If there are crimes committed then we, as a newspaper group, will cooperate fully. But getting leaks from police officers is part of every journalist's job. If every Met[ropolitan] officer was suspended because he'd told a story to a journalist there would only be about six left."
Lowe feels Thames Valley Police did not go through every possible method of obtaining the information, as set out in sections 9 to 14 of PACE, which gives journalistic material special protection. The warrant, seen by Lowe, said that to try other methods would "prejudice the investigation".
"This seems over the top," he said. "You don't want police up and down the country raiding offices every time there's a story in the paper they don't like."
Murrer said this week: "I have had a lot of support from colleagues, fellow professionals and from the people of Milton Keynes with whom I have worked for more than 30 years as a reporter."
The Government is planning to overhaul PACE. A consultation paper said the Government was keen "to examine whether the special provisions to access under sections 9 to 14 of PACE require updating to meet 21st century challenges in tackling crime".
The Newspaper Society has alerted members about the consultation. Society of Editors chairman Bob Satchwell said: "Any changes must be subject to proper consideration. It's important for editors to make their views known and to get ready to mobilise their local MPs.
"Too often we see cases where the police seem to ride roughshod over the legal protection for journalists and ignore the fact the media does an important job in informing the public."