Image caption Raymond Gilmour was a member of both the INLA and IRA during the Troubles

A secret agent who infiltrated the IRA for the British security services has said he has been abandoned by MI5 and left with mental health problems.

Raymond Gilmour, who now lives in south-east England, was the only witness in a trial of 35 IRA suspects which collapsed in 1984.

The "supergrass" claims responsibility for saving many lives, but said he lives in constant fear of being killed.

The Northern Ireland Office (NIO) said it could not comment on any individual.

Mr Gilmour, who is from Londonderry and has lived under a false identity for 30 years, claims his MI5 handlers promised him £500,000, a new home, psychiatric support and a pension.

Media playback is unsupported on your device Media caption Raymond Gilmour says he has been left unable to work and in fear for his life

However, he said he was provided with modest accommodation and £600 a month for three years and was not provided with employment. He also said his false identity does not stand up to scrutiny.

He also claims to have suffered alcoholism and post-traumatic stress disorder (PTSD) as a result of his work and has been left destitute.

With the assistance of his MP, who the BBC has decided not to name, he is now taking his case to the Investigatory Powers Tribunal (IPT) - a body which examines complaints against the intelligence services.

Liam Clarke, Belfast Telegraph political editor I would imagine, given this publicity, the security services will probably want to do something to satisfy him, because obviously they have agents working now in Ireland and in Britain in Islamist organisations. I would imagine if I was an agent now I'd be asking my handler 'how will I be looked after if this all goes sour in a year or two?'. I believe there are contracts now which there weren't in his time. According to the handbook on investigatory powers, there are contracts available to agents, so I suppose that will be explored by the tribunal - should he have been offered one?

The IPT said it would never confirm or deny whether it had received a complaint, even if an individual was claiming widely in the media that they had submitted a complaint to it.

Mr Gilmour said he was 17 when he joined the Irish National Liberation Army (INLA) in 1976 as a Royal Ulster Constabulary (RUC) special branch agent.

'Saved countless lives'

He said he then moved to the IRA in 1980 before his cover was blown two years later when police used information he supplied to recover a machine gun.

"I brought the INLA to their knees in Derry, I brought the IRA to their knees in Derry and I saved countless lives," he said.

"If I'm being treated like this after so many years, what do you think people down the chain are being treated like?

"I am living on a knife edge because of my mental health, I have no financial stability, which I was promised - I have nothing."

His decision to testify in the early 1980s led to the arrest of 35 republicans in his native city of Londonderry.

However, the case collapsed when the then Lord Chief Justice dismissed Mr Gilmour's evidence as being "unworthy of belief".

Image caption Ian Paisley Jr said an agent who worked for the government should be protected

He said he was "heartbroken and disgusted" by the judge's comments.

"I knew I was telling the truth, I was told there were deals struck by RUC men behind the scenes that decisions had to be made that wouldn't be palatable for me, so I was going to be the fall guy," he said.

'Totally paranoid'

After Mr Gilmour's testimony, graffiti appeared around Derry saying he would "be got, sooner or later".

He said he continued to be "totally paranoid" that he would be discovered and keeps a gun by his bed.

For some, Mr Gilmour is still remembered as a traitor who was guilty of betrayal.

Former Sinn Fein publicity director Danny Morrison said: "There will be no love lost for him, no sympathy for him and it doesn't come unexpected that when MI5 are finished with people they discard them."

Ian Paisley Jr, the Democratic Unionist Party MP for North Antrim, said he had sympathy for anyone who had risked their life and the government had failed to protect them.

"An agent - that's who we're talking about - who worked for the government in the dirtiest war ever this side of Kosovo should be protected and given his contractual obligations," he said.

Image caption Senior Irish republican Danny Morrison said what had happened to Mr Gilmour was not a surprise

The NIO said it had been the policy of successive governments not to comment on whether or not a particular individual was or had been an agent.

"Anyone who has a complaint about the conduct or proposed conduct by or on behalf of any of the intelligence services can lodge a complaint with the Investigatory Powers Tribunal," said a spokesperson.

"If a complaint falls within their jurisdiction, they will investigate and respond to the claimant."

Watch the full report on BBC South East Today at 18:30 BST on Tuesday or on Sky Channel 963, or catch up on BBC iPlayer.