Press freedom must be protected following the arrest of journalists Barry McCaffrey and Enniskillen born Trevor Birney, an MP has said.

Tory MP David Davis called on the Home Office to "review the policies of data retention by police forces" following the arrest of the two journalists and the confiscation of their phones last year after their involvement in a documentary examining the Royal Ulster Constabulary's handling of the Loughinisland killings.

He added that "without very good reason, data should never be kept from innocent journalists".

Mr Davis said: "Data retention throughout the United Kingdom has been a long running issue, from DNA to fingerprints, from biometric data to personal electronic data - these issues often face tensions between civil liberties, individual privacy and the demands of the police."

Speaking in his adjournment debate in the Commons, Mr. Davis continued: "We all understand a certain amount of data retention is necessary for fighting crime, but by definition this data should be about guilty people committing crimes.

"As far as possible, we should avoid retaining the data of innocent people."

"On the rare occasions it proves necessary, it should be under the strict control of the courts and its use strictly limited.

"Without very good reason, data should never be kept from innocent journalists - it surely cannot be right for police to store data obtained by a warrant that's been ruled unlawful."

Mr. Davis was referring to the Loughinisland case where Mr. Birney and Mr. McCaffrey were arrested over the suspected theft of confidential documents from the Northern Ireland Police Ombudsman's office.

In June, Durham Police dropped their independent probe into the two journalists following a court ruling.

The men had been involved in a documentary film, No Stone Unturned, which examined the Royal Ulster Constabulary's handling of the 1994 Loughinsiland killings by the UVF when gunmen opened fire in a village pub as their victims watched a World Cup football match.

Mr. Davis called for the Government's policies surrounding data acquisition and retention to be reviewed.

He continued: "I therefore urge the Home Office and the Northern Ireland Office to keep a close eye on the developments in the Loughinisland case, and when it's adjudicated, review the policies of data acquisition and retention for the PSNI and other police forces across the country.

"Because this issue is not confined to Northern Ireland, it will impact investigative journalists and whistle-blowers across the whole country.

"Whistleblowers will see cases like this and feel intimidated that the information that they give to journalists is subject to capture and inspection by the police or other agencies of the state.

"Press freedom is at the core of our democratic system, and it must be protected."

Northern Ireland minister Nick Hurd said he could not comment on any ongoing investigations, but said the PSNI is subject to a high degree of public scrutiny.

He said: "There is arguably no police service in the United Kingdom, or even the world, that is more heavily scrutinised than the Police Service of Northern Ireland."

Mr. Hurd added: "We will continue to keep a close eye on this case and continue to keep it under discussion."

On press freedom generally, Mr Hurd said: "The UK condemns strongly any attempts by governments to restrict the freedom of the media to hold those in authority to account or to intimidate, or detain journalists for political purposes."