Justice Secretary Michael Matheson is being urged to come to Parliament and answer questions from MSPs after police carried out "illegal surveillance" in a bid to find out more details of journalistic sources.

Former officer Gerry Gallacher was reported to have been one of those targeted by Police Scotland after concerns were raised the force had failed to follow up information as they investigated the murder of prostitute Emma Caldwell.

Earlier this week, Sir Stanley Burton, the Interception of Communications Commissioner, concluded the force had contravened the Acquisition and Disclosure of Communications Data Code of Practice on five occasions.

The Interception Of Communications Commissioner's Office (IOCCO) conducted a review after fears were raised officers had been ''illegally spying on journalists''.

Mr Gallacher, a former detective, will now raise the matter with the Investigatory Powers Tribunal in a bid to find out more about the police operation.

He told the Sunday Mail: "To be honest, when it was suggested to me that the police had been intercepting my phone information I found it very hard to believe.

"Now that it has been confirmed, I still find it very hard to believe."

Labour is now demanding the Justice Secretary makes a statement to Parliament, setting out what he knew, while the Scottish Liberal Democrats want the issue to be raised in a debate at Holyrood this week.

Graeme Pearon, Labour's justice spokesman, said: "Michael Matheson has said he knew nothing about this case but he has been SNP Justice Secretary for more than a year now, and has been invisible during the biggest crisis of confidence in Scottish policing in generations. This cannot be another policing scandal where he goes missing."

He stated: "Policing in Scotland once had a world class reputation, but it has been dragged through the mud by a series of scandals this year.

"Now we see that the police service in Scotland had carried out illegal surveillance on five separate occasions.

"Serious questions must be asked why police time and resources were used to hunt the source of a story rather than the potentially crucial information that story presented. It suggests a force more concerned with public relations than keeping people safe."

Liberal Democrat justice spokeswoman Alison McInnes said: "The creation of Police Scotland was the biggest shake up of policing in Scotland for a generation and the consequences for people in communities across the country have been enormous.

"In recent weeks, Police Scotland officers were found to have illegally spied in an effort to uncover journalistic sources. We have seen hugely critical reports on call handling services that say staff are under enormous pressure. The first Police Scotland staff report found one third of officers say they are planning on leaving the force. The list goes on.

"It beggars belief that at no point since the creation of Police Scotland have SNP ministers scheduled no debates on the operations and administration of the police in government time."

She insisted: "It is time that the SNP stepped up to the plate and were held accountable for their record on policing. We need to have a full debate on the operations of Police Scotland in government time.

"Given recent events, if the Justice Secretary put down a motion there is a real chance that the Government would lose the vote. The suspicion is that SNP ministers are running scared of their own record on policing."

Assistant Chief Constable Ruaraidh Nicolson said last week: ''Police Scotland can confirm that it did not adhere to the new guidelines covering access to communications data during a recent investigation into alleged serious breaches of information security.''

He added that the force had since taken "robust and rigorous steps" to ensure all applications for communications data are fully compliant with the Code of Practice and all legislative requirements.