Sinn Fein leader Gerry Adams has admitted there are problems over how allegations of criminality were handled by the republican movement in the past.
In a long article on his blog, he also stated that the IRA "inevitably also made mistakes" in its policing of nationalist communities during the Troubles.
Mr Adams again denied there has been any cover-up of sexual abuse by the party – but admitted that victims were failed by this system of paramilitary policing.
He said IRA members were "ill-equipped" to deal with crime in republican areas.
"This included very sensitive areas such as responding to demands to take action against rapists and child abusers. The IRA on occasion shot alleged sex offenders or expelled them.
"While this may have been expedient at the time it was not appropriate. Victims were left without the necessary social service support and abusers without supervision," he wrote.
"It ultimately failed victims and the community alike. That is a matter of profound regret for me, and many other republicans. But these actions were of their time and reflected not only a community at war but also an attitude within Ireland which did not then understand or know as we now do how deeply embedded abuse is in our society."
The Louth TD said the recent allegations made by Mairia Cahill "are of serious concern to myself and Sinn Fein".
"While I refute completely Mairia's allegations against myself and Sinn Fein, it does raise the significant issue of how allegations of abuse had been handled in the past by republicans," he said.
"Anyone who has any information whatsoever about any child abuse should come forward to the authorities and they will have the full support of Sinn Fein.
"That includes Mairia Cahill, who says that there are perpetrators at large who are a danger to children at this time. Whatever information she has on this she should give to the appropriate authority."