Former double agent Martin McGartland has revealed he helped foil an attack on the UDA's Shankill offices and has cast doubt on claims that police failed to act on intelligence to stop a subsequent IRA bomb which killed nine civilians.
Mr McGartland last night told the Belfast Telegraph he had contacted the Police Ombudsman, who is investigating the allegations, to tell him he believes they are "totally untrue".
The ex-agent revealed that, 18 months before the IRA bomb exploded in Frizzell's fish shop in October 1993, he warned his handler of an imminent attack by the Provisionals on the upstairs offices where UDA leaders met.
Mr McGartland said that RUC Special Branch acted immediately to stop that attack and nearly blew his cover with the extensive measures they took.
"When the chief constable says the police had no information which could have prevented the Shankill bomb, I believe him," the former agent said. "I've no love for the Special Branch or any part of the intelligence services over how they have treated me.
"But I have to say that they acted on every piece of information I ever gave them. When I told them of an IRA plan to bomb the Shankill in early 1992, they left no stone unturned in their efforts to stop the attack - which they did.
"I feel so strongly about this that I've contacted the Ombudsman. I've advised him to check police files to verify how police acted to prevent the 1992 attack."
Mr McGartland said he found it "incredible that the same force would then ignore information from another agent about a bomb attack on the same building" a year later.
On Tuesday, Chief Constable George Hamilton dismissed claims the RUC had advance warning of the Shankill bombing in which seven men and women, and two schoolgirls, died. One of the IRA bombers, Thomas Begley, was also killed in the explosion.
The chief constable was responding to allegations in the Irish News that the IRA's north Belfast commander in 1993, a Special Branch informer known as AA, had told his handlers of the planned attack at Frizzell's fish shop. The Police Ombudsman is investigating the matter.
Mr McGartland (46) worked for four years for Special Branch under the codename Agent Carol. He said that in early 1992, a senior Provisional in west Belfast told him that two IRA bombers were set to hurl coffee jar bombs packed with Semtex into the premises where UDA commanders met.
The IRA leader confided to the agent how the bombers would be dropped off 20 yards from the building and the driver would remain in the getaway car with the engine running. The men would throw the coffee jars into the first floor offices, then escape.
"I wasn't involved in the operation, but I heard all the details," Mr McGartland said.
"I called my handler and told him I believed the attack would take place within 48 hours.
"I had hardly left the phone box when I heard DMSUs (Divisional Mobile Support Units) racing into the area.
"Checkpoints were set up on all roads from nationalist districts into the Shankill. Lanark Way had a permanent checkpoint for days. Police Land Rovers were parked in lay-bys on the Shankill.
"The police's response was so big and so quick that I feared it would blow my cover."
Mr McGartland, who was later abducted by the IRA but escaped and now lives in England, said the security services had "shafted" him after his resettlement.
"But I still have to say that Special Branch were totally conscientious regarding all the intelligence I gave them," he added.
"Their first priority was always saving lives and that came even at the price of jeopardising an agent's security,."
Mr McGartland was a petty criminal who was asked to join the IRA by Special Branch.
His autobiography, Fifty Dead Men Walking, was dramatised in a film in 2008.