The suspected child-abusing brother of Sinn Fein leader Gerry Adams worked for the party in Belfast after being forced out of a branch in the Louth over the allegations, Sinn Fein admitted yesterday.
The local organisation in west Belfast was unaware of claims against Liam Adams even though his party-president brother says he earlier moved to have him thrown out of the party over child protection fears.
Liam Adams is wanted by Northern Ireland police over claims he sexually abused his daughter.
Party chairman Declan Kearney said: "In light of the allegation made public against Liam Adams and the above facts, it is clear that he should not have been a member of Sinn Fein."
Gerry Adams had claimed his brother had been dumped from Sinn Fein at a stage when archive photographs appeared to show him still active in the party.
A report was given to the party's ruling Ard Chomhairle yesterday morning.
Mr Adams's brother Liam was accused of abusing his daughter in 1987 and the alleged crimes were reported to the RUC.
In a statement last night Mr Adams said he went to the PSNI three years ago: "There was no cover up by me. The statutory bodies, including the RUC, were told about this allegation in 1987.
He added: "I made a statement to the PSNI in support of her (his niece) and against my brother."
In his statement, Mr Adams said his brother Liam became a member of a cumann in Lower Anderstown after he had got him to leave Sinn Fein in Co Louth.
Said Mr Adams: "Liam knew the basis on which I had pressed him to leave Sinn Fein in Louth. His decision to re-involve himself in Sinn Fein in Belfast is reprehensible.
"Had I known he was in Sinn Fein in Belfast, I would have acted to have him leave the party."
He added: "Sinn Fein did not know of the allegations against Liam Adams and did nothing wrong.
"There was no cover up by Sinn Fein."
However, Republicans in Belfast last night found it difficult to believe that Gerry Adams, the president of the party, would not know if his brother was involved in a cumann in the city.
"That cumann meets in the Felons Club.
"It is very hard to believe Gerry would not know if his brother was there attending Sinn Fein party meetings there, said one Belfast Republican last night."
Mr Kearney said: "The local organisation was unaware of the allegation against Liam Adams and the circumstances of his departure from Sinn Fein in Louth.
"Clearly his admission to the party in Belfast should have been avoided.
"Gerry Adams has informed the party that he was not aware of Liam Adams involvement in party work at this time."