British military intelligence exploited paedophilia within Gerry Adams' family to get some of his relatives to spy for them, a new book with access to military intelligence sources has claimed.
Stephen Grey is an award-winning writer with extensive military contacts and a record for unearthing embarrassing stories.
Now with Reuters, he is best known for exposing the USA's policy of extraordinary rendition.
His latest book, The New Spymasters, argues that British intelligence perfected agent recruitment in Northern Ireland.
"Cold war espionage was almost all based on volunteers because it was hard to meet people privately in Eastern Europe," Mr Grey said yesterday. "They hardly recruited anyone and the stories that they did tell were mainly propaganda. In Northern Ireland they perfected skills in recruiting people, and befriending them."
He writes: "The collection of intelligence on Gerry Adams, who ended up on the Provisional IRA's four-man Army Council, as well as later leading Sinn Fein, illustrated their methodology.
"His family, they discovered, had a major weakness: his father, the revered Gerry Adams Senior, was a paedophile.
"It later emerged that the IRA leader's brother was too and that he had abused his own daughter.
"The details of the extensive covert operation to exploit that weakness in the Adams family will probably become public at some point, but not here.
"Suffice it to say, the extent of co-operation with the British from a few immediate members of the Adams family has been a well-kept, long-term secret."
He refused to elaborate, but the claim is consistent with statements made by Aine, the niece of Gerry Adams, that the police tried to extract intelligence from her when she reported the abuse by her father Liam Adams.
Deputy First Minister Martin McGuinness is mentioned with regard to Frank Hegarty - 'Agent Melodious'.
Mr McGuinness is said to have removed Mr Hegarty as IRA quartermaster and reinstated him. He was identified as an agent when Libyan weapons were seized.
Mr Hegarty was taken out of Northern Ireland by his handlers but returned and was killed. The book repeats claims Mr McGuinness encouraged him to return when Mr Hegarty phoned his mother. Mr Grey claims these calls were recorded by MI5.
Mr McGuinness has consistently denied any involvement.
Also in the book, Mr Grey writes that the Army's most important agent in the IRA during the Troubles - 'Steak Knife' - was identified for recruitment because he had been demoted in the IRA.
He was identified in the media as Belfast man Freddie Scappaticci. Mr Scappaticci denies this.
"In the 1970s, according to British intelligence, this man killed a British soldier, or certainly wounded one," Mr Grey states.
"For some reason, Steak Knife then fell out of favour with his commanders. While he retained his connections, he was relieved of command. This slight was a weakness that made him a target for recruitment."
Mr Grey believes that the agent got about £300 each time he met his handlers. Another motive was that he got on with them and felt he was in a team.
He writes: "Ultimately, things probably worked out because Steak Knife and his handlers just clicked. As someone well informed said, 'They have to like you. Steak Knife liked football; he liked drinking; he liked music. His handlers liked football, drinking and music too'."