IRA murder victim Jean McConville did pass information to security forces, the IRA has claimed in a statement.
Jean McConville was abducted and murdered in 1972
Mrs McConville was abducted, murdered and secretly buried in 1972.
In a statement, the IRA insisted a "thorough investigation" confirmed that the mother of 10 "was working as an informer for the British army".
Her daughter said the IRA statement had only caused them more pain. A police ombudsman inquiry found no evidence Mrs McConville had ever been an informer.
Police Ombudsman Nuala O'Loan said on Friday they had extensively examined intelligence available at the time and found no evidence Mrs McConville had ever passed information to the security forces.
This was welcomed by Mrs McConville's family, including her daughter, Helen McKendry, who said the ombudsman had confirmed what the family had always known - that their mother was an innocent woman.
However, after the IRA released its statement on Saturday, she said she was not surprised at their insistence her mother was an informer.
"They can't put a statement out saying they murdered an innocent woman, so this is their way of justifying what they did," she said.
"We thought things would die down and we could get grieving and get some sort of peace but there's always something brings it back."
The IRA said its inquiry was in response to a "public request" from Mrs McConville's family.
Jean McConville's remains were found on a County Louth beach
It said the conclusion had been reported to her son, Michael.
"The IRA accepts that he rejects this conclusion," it added.
"The IRA regrets the suffering of all the families whose loved ones were killed and buried by the IRA."
In 1999, the IRA admitted they had killed Mrs McConville and several other of the "Disappeared", but alleged some of them had been informers.
Mrs McConville, who was a widow, was killed after she went to the aid of a fatally wounded British soldier outside her home in west Belfast's Divis flats.
Her remains were finally found at Shelling Hill beach in County Louth in the Irish Republic in August 2003.
In response to the IRA statement, SDLP leader Mark Durkan said "no real credibility will be attached to (the IRA's) continued attempts to malign the memory of Jean McConville".
He added: "I hope the McConville family can take comfort from the fact that decent people fully accept the verdict from the police ombudsman and are likely to be cynical about another self-serving version of events from the IRA."
On Friday, the police ombudsman said it was not her normal role to confirm or deny the identity of people working as agents for the security services.
"However, this situation is unique. Jean McConville left an orphaned family, the youngest of whom were six-year-old boys," Mrs O'Loan said.
"The family have suffered extensively over the years, as we all know, and that suffering has only been made worse by allegations that their mother was an informant."
The bodies of four of the "Disappeared" - people abducted and murdered by the IRA - have been recovered. Five more have not been found.