One in four in IRA members were informers Smithwick Tribunal told
One in four IRA members, including some in the highest echelons, were informers, a tribunal has been told.
Former garda Owen Corrigan said the RUC and the Army paid "endless sums of money" for poor quality information.
He claimed that the British government were putting such pressure on the security services that they were "grateful for any tittle tattle".
The Smithwick Tribunal is investigating alleged Garda collusion in the IRA murder of two senior RUC officers.
Chief Supt Harry Breen and Supt Bob Buchanan were shot dead in an ambush in south Armagh in March 1989 as they returned from a meeting in Dundalk Garda station.
At the tribunal on Wednesday, Mr Corrigan, a retired detective sergeant from Dundalk, said the informers congregated at night in the town and travelled to Northern Ireland the following day.
He said they would tell on each other as "they had no sense of loyalty".
Mr Corrigan said he had information that the "execution" of the two officers had been planned months in advance and involved a considerable number of people, yet he had not received any hint in advance that the murders were to take place.
Allegations have been made that Mr Corrigan himself colluded with the IRA in the murders of the officers.
But on Tuesday, Mr Corrigan rejected any suggestion he may have been a double agent working for the IRA.
During Wednesday's hearing, Mr Corrigan, said informers had leaked his name because he was a "thorn in their side".-
He also dismissed claims from security journalist and author Chris Ryder that he had sought payment for potential stories, when he met him in the 1970s.
Mr Corrigan said it was "a scurrilous slur" on his good name. He then claimed that Mr Ryder was a member of MI5 - a claim the journalist has denied.
The former garda was questioned by the tribunal about an RUC intelligence document which named him in 1985 as someone who was passing information to the provisionals.
The source of that document was grain smuggler John McAnulty, who was later tortured and murdered by the IRA.
Mr Corrigan pointed out that although the intelligence had been graded as "believable" by the RUC officers who compiled it, their boss, with whom he had a good working relationship had dismissed it as rumour and gossip.
The tribunal continues on Friday.
Chief Supt Breen and Supt Buchanan were the most senior RUC members to be murdered during the Troubles.