The British Attorney General has confirmed to RTÉ News that immunity from prosecution has been granted to any former secret agent or informant who gives evidence to the Smithwick Tribunal in Dublin.
The Tribunal is investigating whether there was collusion between the IRA and a garda in the murder of the two most senior RUC officers to die in Northern Ireland.
The move will clear the way for former members of the British security forces and those who worked for them in Northern Ireland to give evidence.
RUC Chief Superintendent Harry Breen and Superintendent Robert Buchanan were murdered by the IRA in an ambush shortly after leaving a meeting in Dundalk Garda station on March 1989.
Claims of collusion between at least one garda and the IRA resulted in the Smithwick Tribunal being set up in May 2005.
However, several key witnesses including former members of the British security services and one man who claimed he worked undercover in the IRA have refused to cooperate fully with the Tribunal.
They had claimed that they risked prosecution by revealing what they had done and for breaching the Official Secrets Act.
A memo of understanding has been issued to the Tribunal which states that no one will be prosecuted for any statement they make there except where they are charged with giving false evidence.
