The Taoiseach expressed surprise at a British Ministry of Defence directive to former employees not to co-operate with the investigation into the 1974 Dublin and Monaghan bombings.
Mr Ahern was replying to the Fine Gael leader, Mr Enda Kenny, who said that those who had worked for the ministry in the 1970s had been told not to provide information to the families of the victims.
He added that the directive added to the "suspicion and perception that something is not above board."
Mr Ahern said he was surprised "by both its tone and contents".
He told Mr Kenny that he had the matter raised immediately through the Anglo-Irish Secretariat.
"A response has been received reiterating the Prime Minister's undertaking to respond as positively as possible to Mr Justice Barron's request for material.
It further stated that the British government had made it clear to former employees that the decision on whether to co-operate with Mr Justice Barron's inquiry was a matter for the individuals concerned and not a matter for the British government.
"I hope Mr Justice Barron will receive all the information he requires from all sources."
Mr Ahern revealed that the report of the inquiry is expected to be completed early next year.
He added that he had raised the issue of the co-operation of the British authorities with the Prime Minister on a number of occasions.
Pressed by Mr Kenny to consider establishing a formal inquiry to investigate the decisions which lay behind the bombings, the Taoiseach said he was not aware of the information which the commission had gathered to date. It was entirely independent.
"As soon as we see the report, I will honour my commitment to bring it to the relevant committee, after which we will have to examine the options."
