EXCLUSIVE: Cardinal Keith O'Brien is facing legal action stemming from new allegations of sexual misconduct, with a former trainee priest claiming he was abused by the disgraced cleric as a teenager.

The former seminarian, who had known the cardinal since childhood and is the first to speak publicly of his experience, said he had only broken a 30-year silence after recent revelations about the former archbishop's sexual behaviour made it clear his ordeal was not an isolated episode.

The allegation relates to a period in the 1980s when the man attended a senior seminary college, following four years at Aberdeen's Blairs College for trainee priests.

He left the priesthood several months after Cardinal O'Brien, who was then rector of Blairs, allegedly groped and kissed him during a visit to the unnamed seminary.

Speaking exclusively to The Herald, the former seminarian, who is now in his 50s and has asked to remain anonymous, said he had instigated legal proceedings against both the cardinal and the Catholic Church.

The victim says he is prepared to face "Keith" in a courtroom in the hope his actions will encourage others, who may have been reluctant to complain about similar experiences, to come forward.

His solicitor has described his client as "totally credible" and his claims as "consistent and measured".

Cardinal O'Brien has gone to ground following claims nearly three weeks ago that he "behaved inappropriately" towards three priests and a former priest in the 1980s.

Following the revelations, he was stood down from his post as archbishop of St Andrews and Edinburgh and subsequently admitted his sexual conduct had "fallen below the standards expected of me as a priest, archbishop and cardinal".

The victim claims it was only in the aftermath of the revelations that he eventually told a lifelong friend, another former trainee priest, of his experience as a 19-year-old.

He described the unfolding events of the past fortnight as "like forcing myself to watch a movie I don't want to see" and said it had been "near-impossible to appear normal" since the full magnitude of events emerged.

Until the revelations came to light he had put the cardinal's alleged conduct down to a one-off act of weakness, but now believes it was premeditated and part of a pattern of behaviour.

The man, who later married and had children and a successful career away from the Church, said Cardinal O'Brien invited him to his room in the 1980s after dinner in the seminary, adding: "We'd some sort of drink in his room, beer or wine. He was just chatting away about the past, the future and so on.

"He had been talking about himself, how he was going places, his career had been mapped out and that it was for God to decide. I can't remember the exact phrase he used but he told me he would always look after me and how good a priest I'd be. Until this stage I'd thought how excellent it would be to be a priest in his diocese.

"But that's when it happened...after a few minutes he released me and I was able to make my excuses and go. As an adult looking back I ask myself how it could have happened. Neither of us was drunk."

His solicitor, Cameron Fyfe, said: "I have been instructed to make a claim for compensation against Keith O'Brien and his Archdiocese on the basis of abuse my client suffered at his hands in the 1980s while at seminary.

"I am currently preparing the case but hope in all the current circumstances that the Church may take a reasonable stand and consider settlement of the claim without the expense and trauma of a court action.

"I have acted for over 1000 clients who have been victims of sexual and physical abuse. Over the years you learn to assess credibility. I have found this client to be totally credible. The information he has passed to me is consistent and measured. If the case does eventually require to go to court I think he would be an excellent witness."

The former seminarian is to undergo psychological assessment in the coming weeks, which could corroborate his claims, with Mr Fyfe suing for both the trauma and loss of career.

Similar claims in the past have led to payouts in excess of £50,000 in cases involving clerical and other abusers.

The man added: "When I spoke to the lawyer I broke down. I haven't been sleeping, I've been physically sick. If I didn't have any children I'd have no problem with anonymity. But at this stage I believe I would be prepared to face Keith in a court room.

"I know the truth. I'd still refer to him as Keith and ask him as a religious man under oath is he prepared to deny what I'm saying is the truth."

A spokesman for the Catholic Church in Scotland said: "The Church is disturbed to hear of these allegations. Any complaints raised will be taken very seriously."