Transcripts of telephone calls between the Taoiseach and the British Prime Minister were found in the possession of republican activists in the North, the Dáil was told.
Mr Ahern said he had not seen any documentation, but he had been briefed on the matter. He added that a review of confidential documentation was now being undertaken in a number of Departments, including his own.
The matter was raised at Question Time by the Labour leader, Mr Ruairí Quinn, who asked the Taoiseach: "Can the Taoiseach confirm that the British government showed him transcripts of conversations which took place between senior Irish and British Ministers about bilateral discussions, which were in the possession of Sinn Féin and/or the IRA ?
"Will he confirm or deny that such information was shown to him by the British authorities ? Will he make known to this House that now, 4½ years after the Good Friday agreement was signed, and 2½ years after complete decommissioning was called for, it might be constructive and desirable if there was an all-party resolution by all of the parties in this House, that all paramilitary activities cease and all paramilitary activities cease and all paramilitary organisations be stood down by their parent political organisations ?"
Mr Ahern replied: "In reply to Deputy Quinn's question, I was not shown any documents, but it is correct to say that I was briefed that documents and transcripts existed and I have no reason to believe that is not the case. They were, as he outlined, sensitive documents."
Asked by Mr Quinn if the Taoiseach was involved in any of them, Mr Ahern replied: "The documents were of the scale the deputy refers to, including transcripts of calls between myself and Prime Minister Blair."
The Fine Gael leader, Mr Enda Kenny, asked Mr Ahern if he had any reason to believe that information from his own office, and from other Government offices, including transcripts and communications, was not being filtered away to sources that should not have them.
Asked about developments in the North, Mr Ahern said the institutions had broken down, because, once again, trust had broken down between the parties. There would have been a suspension of the institutions, even if the British government had not acted because the Ulster Unionist Party was clearly going to pull out, he added.
"In an honest and fair way, we now must try to build it up as quickly as possible, working with all the parties because there is no use being involved in the blame game. We must move on and find the terms that will allow the parties to get back in partnership, working together in mutual trust and confidence. It is never easy to do, but I detect from all sides a willingness to try." Mr Ahern said the Government's considered view, which it shared with the British government, was that all paramilitary groups should be out of the equation.
"Most of the violence in recent times has been from loyalists not from republicans, but there is still the issue of trust, and, until all sides move away from that, it will be very hard to get stable institutions, which is what we want to achieve." Mr Ahern said he was anxious to organise a session of the Forum for Peace and Reconciliation before Christmas.