A retired undercover police officer has broken his silence on his career, saying his job caused him to suffer from post-traumatic stress disorder.

The former detective attacked the poor welfare arrangements for undercover officers in the field and said failures by the police led to the breakup of his marriage.

The Scot, who this newspaper is referring to as “Peter” to protect his identity, said he raised his concerns with the now defunct Scottish Crime and Drug Enforcement Agency (SCDEA) but claimed his pleas were ignored.

The ex-officer, one of the few advanced undercover operatives from Scotland, also described a police Inspectorate review into the tactic as an “absolute whitewash” and called for a Scottish public inquiry.

He also hit out at the “absolutely appalling” tactics of officers in units south of the border - such as using the names of dead babies for cover names - which he said had discredited undercover policing.

A judge-led inquiry is looking into the practices of two London-based units - the Special Demonstration Squad (SDS), and the National Public Order Intelligence Unit (NPOIU) - following huge public concern over their behaviour.

Notorious "spy cops" like Mark Kennedy and Bob Lambert infiltrated peaceful campaign groups, had sex with the women they spied on and vanished after inventing stories about mental health problems.

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However, although the SDS/NPOIU operated in Scotland, the inquiry is restricted to England and Wales. Justice Secretary Michael Matheson instructed Her Majesty’s Inspectorate of Constabulary in Scotland (HMICS) to carry out a “review”, but campaigners were left furious after undercover policing was given a clean bill of health.

Peter, who is now retired from the Scottish police, contacted this newspaper after being angered by the HMICS review.

The former officer started in the military and joined one of the old Scottish constabularies in the early 1990s. He joined the Drugs Squad and became interested in covert policing.

Peter then applied for the elite S010 course at the national undercover training assessment centre in London.

“It actually took me the guts of two years before I put my bum on the seat at the course,” he recalled. “The application process is very lengthy. You go through a local a board, a national board, psychometric testing, then a final board.”

Around twelve officers were on his course, but only a handful passed. “You are put under immense amount of stress - and rightly so," he said. "The course is not designed to test you as a police officer. You have proved you are a good police officer. It’s about how you would react in highly stressful situations.”

He passed - one of the few Scots to do so - and he became part of a UK pool of undercover officers who could be deployed across the country.

His “host unit” was the SCDEA, and later Police Scotland, which had oversight of undercover officers from Scotland. He did not work for the SDS or NPOIU, although his operations were south of the border.

Peter will not talk about the detail of his deployments, but he worked on around 25 projects from 2003, all of which focused on the "higher echelons" of organised crime. His specialism was infiltrating drug importation groups and his longest deployment was for two years. He was not involved in spying on protest or campaign groups.

“I was fluent with all the translations of weights, amounts and prices. I sat many a time arguing with a drug dealer about the cost of how much he was going to supply me with a kilo,” he said.

Peter said his work as a “UC” had a “massive positive effect” and led to criminals going to jail. “Undercover police officers are driven because they want to see serious and organised criminals go to prison,” he said.

There were occasions, he told the Sunday Herald, when the groups he targeted quizzed him about his background: “I have been sat down and interrogated.”

However, Peter said he suffered a huge personal toll from living a double life for over a decade: “I knew I was suffering from isolation. I was really struggling to put my pseudo identity back in the box. I thought I was managing it all, but I couldn’t manage it.”

He added: “I was told by friends repeatedly to go and see a doctor. I was scared to admit weakness. From 2008, I started to suffer from post-traumatic stress disorder.”

He was also away from home for extended periods of time and his marriage eventually broke up: “I was shoving my family away.”

Peter said a vital component of undercover policing is the wellbeing of the officers in the field. At a minimum, he believes they require fortnightly visits from welfare specialists and twice-yearly contact with a psychologist.

However, he said the record of the SCDEA and Police Scotland on this front was “poor and at times non-existent”. He said: “I should have had twice yearly psychology tests. Over that period [13 years] I think I saw a psychologist five times.”

In 2011, after the Kennedy scandal was exposed, Peter outlined his concerns to the SCDEA professional standards department about the welfare arrangements for covert officers.

He wrote at the time: “I was totally let down by the unit during lengthy and hazardous deployments and believe this has contributed to the breakdown of my marriage. I believe that it is only good fortune that no one was compromised or injured during this time, as the mechanism to protect UCs was clearly not there.”

Peter said the HMICS review, which was positive about the welfare aspects, amounted to “brushing a huge amount of shit under the carpet” and described the findings as an “absolute whitewash.”

A member of the HMICS review team was former senior officer Stephen Whitelock, who used to be the deputy director of the SCDEA.

Peter said Whitelock’s role on the review, including carrying out interviews, was a “conflict of interest” and he believes “100%” that there should be a Scottish inquiry: “There has to be a transparent process where the mechanics of undercover policing are looked at with a fine tooth comb, not just a 62 page document.” He said an inquiry would benefit victims of undercover policing and officers whose welfare needs were overlooked.

Looking back on his career, he is angry about the damage done to the reputation of undercover policing by the SDS and NPOIU.

At an undercover training course, he came across some of the SDS officers, including Mark Jacobs, who infiltrated various left-wing groups. He said that the SDS officers were “flippant” and like “giggly kids”.

Peter said of his reaction to the Kennedy revelations: “I was really quite disgusted in Mark Kennedy and the management of that group. It absolutely destroyed undercover policing.”

His own method of developing a cover name - known as a “legend” - was straightforward, so he is scathing about the practice of taking the identities of dead children. “Why would I want to discredit someone who has passed away?” he asks.

On undercover officers sleeping with the female protesters they were spying on, he said bluntly: “It is rape.”

He concluded: “It’s totally beyond me and a disaster of their own management structure. It’s absolutely off the scale.”

Labour MSP Neil Findlay said: “These are damning revelations from someone who worked as an undercover officer. I have always felt that the HMICS review amounted to the police marking their own homework. The words of this undercover officer show that he also feels this happened. How can anyone have confidence in the outcome of that review?”

A spokesman for HMICS said: “As highlighted in our terms of reference, HMICS provided an independent view of the safeguards in place by Police Scotland in respect of undercover policing. This included a thorough review of the welfare and support arrangements currently in place for undercover officers and led to recommendations within our report, which will strengthen these arrangements. In terms of legacy forces, including the SCDEA, our remit was only to establish the extent and scale of their undercover policing operations.

“We were also explicit within our terms of reference that the review would be led by HM Chief Inspector of Constabulary, Derek Penman and that he would draw on the experience and expertise of a number of people, including staff from within HMICS and others who were independent of policing in Scotland. Measures were put in place to protect the overall integrity of the review and all team members were deployed appropriately into specific areas where there could be no conflict of interest.”

Police Scotland Assistant Chief Constable Steve Johnson said: "The welfare of all of our officers is paramount and we take great care to ensure that officers who undertake the sometimes dangerous work of undercover policing are fully supported. This was recognised by HMICS when they published their report into Undercover Policing in Scotland last month, and we are implementing their recommendation to further enhance that support by employing an additional human resources specialist for such staff. "