SINN Fein president Gerry Adams said that the IRA acted as a police force in Northern Ireland during the Troubles and said that alleged sex offenders were shot on occasion.
The TD's statement was issued last night amid claims by Mairia Cahill that she was raped by a senior IRA man when she was just 16 years old.
Ms Cahill said she was later interrogated by the IRA about the incident, which happened in 1997.
She later went to the police and a case was brought against the alleged rapist, which subsequently collapsed.
Sinn Fein president Gerry Adams has described how the IRA acted as a police force in Northern Ireland during the Troubles.
Mr Adams said the IRA often punished petty criminals, car thieves, burglars and drug dealers - in the absence of a civic police service.
"The IRA on occasion shot alleged sex offenders or expelled them," he added.
Mr Adams said that there was a "rough justice" before it took time for a new justice system to evolve.
"There was also, particularly in the first two decades of the conflict, a more brutal form of rough justice," he said.
He said while certain IRA policing activities may have been expedient, at the time it was not appropriate.
"Victims were left without the necessary social service support, and abusers without supervision. It ultimately failed victims and the community alike," he said on a blog.
"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."
Mr Adams said that the IRA were "singularly ill-equipped to deal with matters" such as sexual abuse and rape.
"The recent allegations made by Mairia Cahill are of serious concern to myself and Sinn Fein," he said.
"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."
Adams said the IRA has "long since left the scene" so there is "no corporate way of verifying" Ms Cahill's claims that the IRA investigated the allegations.
But he said anyone with information about child abuse, including Ms Cahill, should come forward to authorities.
Meanwhile, Fianna Fail leader Micheal Martin has claimed a culture of "omerta" exists within Sinn Fein.
In a clear reference to the party's historic links with the IRA, he said this is stopping members from speaking out against "darker elements" from its past.
Addressing the annual Fianna Fail Wolfe Tone Commemoration ceremony in Bodenstown, Co Kildare, he claimed so-called "modern faces" within the party, are "happy to collude" in this approach.
Mr Martin said Sinn Fein's effort to promote an "unbroken chain" from earlier revolutionaries to the modern day party is both sinister and dangerous.
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