Gerry Adams told the sister of a man left to bleed to death after a so-called punishment shooting that the IRA men behind it would not be reported to the police, it has been claimed.
Andrew Kearney was shot three times in the leg after a west Belfast bar brawl in which he punched an IRA man in 1998.
His sister Eleanor King is still seeking justice.
She has revealed in an RTE documentary about paramilitary attacks, Above The Law, how the Sinn Fein leader apologised privately for the IRA killing.
However, he refused to make it public.
"The first thing he told us was that he was extending an apology from the top of the republican movement," Ms King said.
Asked by Mr Adams what she wanted, Ms King said her mother requested the gunmen be handed over to the police and for justice to take its course.
"But I think at that stage he told her that it wouldn't happen," she said. "That they wouldn't be handed over but that they would deal out any discipline that was forthcoming from them."
Above The Law is on RTE One at 9.35pm tonight