POLICE Scotland’s elite anti-corruption division used its spying powers in a bid to uncover a journalist’s sources without getting judicial approval.

The Sunday Herald can reveal that the force’s Counter Corruption Unit (CCU) – dubbed a “secret police force” by critics – is being probed by a surveillance watchdog over a violation criticised by the Prime Minister.

The revelation has fuelled criticism of the single force, whose embattled chief constable Stephen House is under pressure to resign over a barrage of issues.

A row broke out last year after it emerged that police forces in the UK had been using the Regulation of Investigatory Powers Act (RIPA) to access journalists’ phone records, texts and emails.

The RIPA powers allow officers to identify the “who, where and when” of communications data, rather than the content. Internal approval by police officers is required before the data can be provided.

Campaigners argued that the practice infringed Article 10 of the European Convention of Human Rights, which covers freedom of expression and protects journalistic sources.

The revelations prompted the Interception of Communications Commissioner Office (IOCCO), which monitors the use of the RIPA, to investigate the extent of the snooping on reporters across the UK.

IOCCO became aware of 34 police investigations over a three-year period, covering the relationship between 105 journalists and 242 sources.

A majority of the applications, the Commissioner concluded, failed to justify the principles of “necessity and proportionality”.

In March, the RIPA was amended to require that a revised Code of Practice protected the public interest in the confidentiality of sources.

The Code now requires police forces to obtain judicial approval before using the RIPA to identify a journalist’s sources.

However, IOCCO last month revealed that two unnamed forces had breached the revised Code since March 25.

It said: “Two police forces have acquired communications data to identify the interactions between journalists and their sources in two investigations without obtaining judicial approval.

“These breaches were identified during our inspections. In these cases the normal RIPA process was used and the data was approved by a designated person.”

In one of the cases, a force acquired the data of a newspaper’s suspected source and of a former police employee believed to be acting as an intermediary.

IOCCO described the breaches as “serious contraventions” of the Code, while Prime Minister David Cameron also criticised the “serious” matter.

Since the IOCCO report was published, Police Scotland has consistently refused to deny that it is one of the two forces.

However, a source has told this newspaper that the breach occurred within the single force’s CCU.

The insider said the breach is being investigated by IOCCO and that the Unit is under the spotlight.

It is understood the case may relate to a public interest story on a well-known murder.

A figure who had helped the newspaper received a police “calling card” after the article was published.

The CCU has two key roles: to root out corruption in the police force; and prevent similar criminality across the wider public sector.

Around 50 officers and staff work inside the Unit.

However, some police insiders believe the CCU spends too much times on trivial data protection issues and lacks accountability.

In January, it was claimed that Police Scotland had wasted around £500,000 of public money in the course of the failed prosecution of officers Amanda Daly and Andrew Reid for an alleged data protection breach.

The pair were acquitted after dozens of court appearances.

Daly’s lawyer, Aamer Anwar, blasted the CCU at the time. He said: “Within Police Scotland there is the perception that there is no accountability or transparency of the Counter Corruption Unit, in that they are responsible for investigating complaints against themselves.

“It is hardly surprising then that ordinary police officers feel that they are a ‘law unto themselves’. One insider claimed the CCU was a “secret police force” in all but name.

Willie Rennie, the leader of the Scottish Liberal Democrats, said: “Police Scotland are not above the law.

“Neither the Scottish Government nor Police Scotland should hide behind the commissioner of the UK Government on this important matter. They have the power to tell us what happened.”

Scottish Conservative chief whip John Lamont said: “It’s essential in Scotland ?that the media is free to hold public life to account.

“That includes Police Scotland, and a situation whereby the single force was spying on journalists to work out their sources would be entirely unacceptable.

Nicola Sturgeon must make clear what she knows about this and what, if any, action she plans to take.”

A spokesperson 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.”

Asked if the First Minister had been informed that Police Scotland was one of the forces referred to in the IOCCO report, a Scottish Government spokeswoman said:

“Under current constitutional arrangements, obtaining telephone records (communications data) is a matter reserved to the UK Parliament and the Interception of Communications Commissioner reports on it to the Prime Minister.

“The policy of IOCCO is that it does not identify agencies where breaches have occurred.”