Martin McGartland, a former RUC Special Branch agent within the IRA, has confirmed claims that the Provisionals got co-operation from people working for the RUC.
It is claimed a honey trap involving one of the Provos' very own Mata Hari was used to seriously compromise police security.
The disclosure comes just days after the Belfast Telegraph revealed details of a top secret document from an intelligence whistleblower which claims the IRA ran agents in the police.
The dossier of evidence from Ian Hurst, a former member of British military intelligence who also claims half of all senior IRA members were working for various intelligence services, was given to the Smithwick Tribunal investigating Garda collusion in the IRA murder of top RUC officers Harry Breen and Bob Buchanan in 1989.
McGartland, who is now living in Britain under a new identity, revealed: "In early 1990 I couriered information which a police officer provided to IRA intelligence."
The incident happened about a year before he escaped an IRA interrogation squad by jumping out of a fourth floor window in Twinbrook in west Belfast.
He had been asked by both his handlers and his IRA commander to work with Rosena Brown, an actress and Sinn Fein worker.
"Rosena was very well-spoken and pleasant to deal with, but she was old enough to be my mother," he said, denying claims in the film Fifty Dead Men Walking, which portrayed them as having a romantic relationship.
"She took a package wrapped in clingfilm out of her mouth and told me to bring it to Davy Adams," he added.
Davy Adams, a cousin of Sinn Fein president Gerry, was an IRA leader and friend of McGartland.
Adams opened the package and read the contents before asking McGartland to bring it to an IRA intelligence collator in Turf Lodge.
However, Adams didn't take the normal IRA precaution of sealing the clingfilm with a lighter and this enabled McGartland to open and read it. "'RUC' was written at the top and the rest of the document was a list of about a dozen police officers," he said. "It had their names, their full addresses, their post codes and car registrations and looked like it had been copied off a police database of some sort."
McGartland had not time to copy the note, but as soon as he dropped it off he phoned 'Felix' and 'Mo', his police handlers, for an emergency meeting and told them what he could remember.
"When I next met them they told me they believed she (Brown) had formed a relationship with a police officer who was supplying her information," he said.
As far as he knows, no action was taken. However, Brown was later dubbed the 'IRA Mata Hari' after being named in the trial of John Christopher Hanna, a prison officer, whose confidence she won by a mixture of blackmail, political argument and seduction.
In return he provided her with information on his colleagues, which, the court found, led to the 1988 murder of Brian Armour, a prison officer at the Maze.