AINE Adams claims that her uncle Gerry wanted her allegations of sex abuse against her father kept a secret from the police and the public.
And the child abuse victim's mother has revealed that the Sinn Fein leader had given his niece "false hopes" that something was going to be done about her father's behaviour.
Aine Adams and her mother Sally make the claims in a special 'Insight' documentary which is to be re-broadcast tonight on UTV.
The investigation, by award-winning journalist Chris Moore, originally aired in December 2009, contains serious allegations which will ratchet up the controversy surrounding Gerry Adams' role in the abuse scandal.
In the 'Insight' programme Aine describes how she and her mother first told Mr Adams about the allegations in 1987 – but that he took no action for 20 years until the police investigation was re-opened at her request.
The 40-year-old mother also reveals how she was approached by campaigning priest Fr Aidan Troy on behalf of Liam Adams the night before Liam was to be formally interviewed by police. Following the interview, Liam Adams went on the run.
"He (Fr Troy) said Liam would have met with me and do whatever it took but don't go to the police because the media would have a circus," she claims.
Fr Troy, who gained worldwide recognition for his role in the Holy Cross primary school dispute, refused to comment about the allegations when they were broadcast four years ago.
Aine describes a series of meetings she had with her uncle after she decided to resurrect her original police complaint against her father in 2004.
Gerry Adams said that he was trying to get her father to apologise to her face-to-face but he never turned up.
She says: "I got my eyes opened because when I was going to the meetings it was turning into Liam was the victim. 'Our Liam is sick in the head . . . our Liam can't deal with what he did to you . . . that's why our Liam is sick in the head now . . . our Liam can't cope."
Aine claims her uncle told her: "I'm trying to get him to meet you but you know he's a coward and he may not want to do that (apologise)."
She said that she believed the meetings were being organised in the hope that she would eventually drop her allegations.
She said she told her uncle: "You have failed me again 20 years later (after first telling him about the abuse). I wrote Gerry Adams a letter telling him that I was stopping contact."