PRESSURE is mounting on ministers to take action on Police Scotland amid further criticism of the force over claims it illegally spied on a journalist to uncover sources.

The force's elite Counter Corruption Unit (CCU) is said to have snooped on the reporter without getting judicial approval - a tactic which was banned on March 25 following a row over officers using the Regulation of Investigatory Powers Act (Ripa) to access journalists’ phone records, texts and emails.

A recent report from Ripa watchdog the Interception of Communications Commissioner Office (IOCCO) revealed two forces have since breached the new code of conduct, and claims have now emerged naming Police Scotland as one of those forces.

The revelation - revealed in our sister title the Sunday Herald - has fuelled further criticism of the single force, which has come under increasing pressure in recent months, and its chief constable Stephen House who has faced calls to resign.

However, despite numerous calls for either Police Scotland or the Scottish Government to confirm whether or not the report does relate to the force, both have refused to do so.

Labour party justice spokeswoman Elaine Murray said: "This is yet another potential scandal at Police Scotland that has happened on Nicola Sturgeon's watch. Sooner or later she is going to have to get a grip on policing in this country.

"We need to know urgently what Nicola Sturgeon knows about these allegations and what she is going to do about them. As First Minister the buck stops with her."

Ms Murray added that there is something "deeply unsettling" about the allegations, claiming that journalists should be free to hold public bodies to account "without the state monitoring their private communications with sources".

The Liberal Democrats have also called for answers and party leader Willie Rennie has written to Justice Secretary Michael Matheson demanding that he reveal whether or not Police Scotland is one of the forces at fault.

The letter states that the claims are of "significant concern" following a difficult period for Police Scotland, adding: "The rules around accessing communications data were changed under the last UK government for good reason. A free press is vital to holding the powerful to account.

"Use of these powers without proper judicial approval is wholly unacceptable. I am aware that neither Police Scotland nor the Scottish Government have confirmed these reports. I would urge you, as Justice Secretary, to show leadership and confirm whether the details reported in the media are accurate.

“If Police Scotland is to regain some of the credibility that has been lost in recent weeks then transparency is vital. You have the power to end the uncertainty over whether Police Scotland accessed communications data illegally. I would encourage you to use it."

Scottish Conservative chief whip John Lamont also urged the First Minister to make clear what she knows and what action she plans to take.

The new regulations were brought in after it emerged Ripa was being used by the UK's police forces to spy on journalists, with 34 investigations taking place over a three-year period, covering 105 journalists and 242 sources.

The Commissioner concluded that the majority of the cases failed to justify the principles of “necessity and proportionality”.

The Ripa code of conduct now requires forces to obtain judicial approval before using the Act to identify a journalist’s sources.

Police Scotland is understood to be the subject of a further investigation by the IOCCO looking at the breach, with sources claiming it may relate to a public interest story on a well-known murder.

The single force has been plagued with controversies since its introduction in 2013 - including issues over stop and search and routinely arming officers.

In more recent times, the death in custody of Sheku Bayoh, which is being investigated by the police watchdog, and the incident involving a crash on the M9 which officers failed to investigate for three days, have also caused problems for the force.

A spokesman for Police Scotland said: “IOCCO has clearly set out its rationale for not identifying organisations in its report, and therefore it would be inappropriate to comment further.”

A Scottish Government spokeswoman said the matter is a reserved issue for the UK Parliament.