A detective has quit amid a probe into claims that details of undercover officers were leaked to an organised crime gang.

Another officer has been suspended as the investigation – led by Police Scotland’s internal Professional Standards Department (PSD) – continues.

The men, believed to be part of Police Scotland’s Organised Crime and Counter Terrorism Unit, have been accused of handing over details of their own colleagues, carrying out covert surveillance, to underworld sources.

It emerged in April that a major inquiry had been launched into the claims, which focus on the Scottish Police College at Tulliallan, Fife.

The Mail can reveal an officer has since resigned – and the other officer remains suspended.

The disclosure comes after the force hailed the 10th anniversary of the Scottish Crime Campus at Gartcosh, Lanarkshire – which brings together agencies combating organised crime – at an event earlier this month (AUGUST), attended by Justice Secretary Angela Constance and Chief Constable Jo Farrell.

Last night Scottish Tory justice spokesman Russell Findlay said: ‘Days after Scotland’s law enforcement community celebrated the 10th anniversary of the Gartcosh crime campus, this shocking episode serves as a reminder about the extreme dangers posed by organised crime.

‘The seriousness of these allegations merits a robust and thorough investigation.

‘Any brave officer whose personal details may have been leaked is entitled to full support and absolute candour about what exactly has happened.’

Former First Minister Humza Yousaf expressed ‘deep concerns’ over the claims of the alleged leak earlier this year, after it was reported that some undercover officers were demanding to know if they were safe to work on criminal investigations.

A Police Scotland spokesman said: ‘One officer remains suspended and one officer has since resigned.

‘Enquiries are ongoing.’

Several addresses across central Scotland have been raided as part of the probe.

One of them is understood to include accommodation used by one of the two suspects at the Police College.

A source told the Sunday Mail earlier this year: ‘These are highly-trained cops who only target organised crime groups and terror cells and use high-level covert surveillance methods to gather intelligence to pass onto colleagues

‘Their operations are expensive and time-consuming and their identities are kept a closely guarded secret for obvious reasons.

‘If the allegations are true then these officers have been seriously compromised.’

It is understood the alleged rogue officers had access to intelligence databases containing sensitive information about police personnel.

The PSD – equivalent to the the anti-corruption unit AC-12 on the BBC’s TV show Line of Duty – investigates complaints from members of the public about officers’ conduct and probes allegations of criminality and corruption within the police.

Undercover officers can also include infiltrating criminal gangs and placing listening devices in vehicles and properties.

There are around 40 officers across the country involved in this type of specialist undercover work, based at the Scottish Crime Campus.

Officers from the unit also have responsibility for airport security, working alongside other agencies.

The Police Scotland website describes the work of the Organised Crime and Counter Terrorism Unit.

It said: ‘Scotland has a combined command for targeting organised crime and dealing with counter terrorism matters. ‘This is structured in teams located throughout the country which target organised crime groups.

‘Officers also work on providing a co-ordinated national response to tackle counter terrorism.’

Earlier this year, it emerged that spending on the PSD had risen by around £4million in the last decade to £8.4million.

A report also showed 15 officers were sacked or resigned from Police Scotland in 2023 after facing gross misconduct charges, and additional officers have been recruited by the force into the department which reflected the increased spending.

The PSD recently investigated a complaint that the wife of murdered Nairn banker Alistair Wilson had been misled over the planned arrest of a suspect.

Veronica Wilson was told that a suspect had been identified over her husband’s 2004 murder and that he would be arrested for questioning.

But the Scottish Mail on Sunday revealed earlier this year that family were later informed that the arrest had been cancelled on the planned date.

Police Scotland has since apologised to the family after three complaints were upheld by the PSD.

Award-winning BBC drama Line of Duty, which stars Martin Compston, Adrian Dunbar and Vicky McClure, is about a police anti-corruption unit which is attempting to identify police officers with links to organised crime.

In one storyline, Detective Inspector Matthew ‘Dot’ Cotton, played by actor Craig Parkinson, was able to infiltrate AC-12 to give information to organised crime groups.