Sinn Fein knew that the IRA was planning the £26.5m Northern Bank raid and other robberies while holding key political talks, Bertie Ahern has said.
Mr Ahern was speaking in the Irish parliament
The Irish prime minister told the Dail that he learned this for the first time when he and Tony Blair were briefed by Belfast and Dublin police chiefs.
"There is no doubt the planning... was going on last year and obviously we were in negotiations then," he said.
NI police chief Hugh Orde has blamed the IRA for the raid. It denies this.
Chief Constable Hugh Orde and Garda Commissioner Noel Conroy delivered their latest security assessment on Tuesday.
Mr Ahern said they told them "a number of operations that took place during 2004 - not just the Northern Bank robbery - were the work of the IRA, had sanction from the Army Council and would have been known to the political leadership of the IRA".
The taoiseach told the Irish parliament on Wednesday that the two governments were waiting for answers from republicans to the questions they posed on decommissioning, and on ending paramilitarism and criminality.
Meanwhile, Sinn Fein has accused Tony Blair of "talking nonsense" when he said IRA activity was the only obstacle to political progress.
Martin McGuinness said this was a "silly statement" as "everyone was aware of the DUP's failure to commit to powersharing".
He was speaking before a Sinn Fein delegation met Secretary of State Paul Murphy.
Mr McGuinness said the DUP had failed to commit to powersharing
Mr Murphy also met an Alliance Party delegation at Hillsborough Castle on Wednesday.
Prime Minister Tony Blair said on Tuesday that ongoing IRA activity was the "obstacle to a lasting and durable settlement in Northern Ireland".
He was speaking after meeting Mr Ahern at Downing Street to assess their political options in the wake of the Northern Bank raid in Belfast in December.
The Independent Monitoring Commission's report on the robbery is expected to be sent to the governments this week.
The ceasefire watchdog's report is expected to confirm the police assessment that the IRA was behind the raid, and to recommend certain sanctions.
The two prime ministers' meeting was seen as their most significant since they launched their joint proposals for the restoration of devolution in Northern Ireland in December.
The two governments have been considering their strategy for the coming year.
It is understood they believe an all-inclusive executive is impossible without a complete end to IRA activity.
The four Independent Monitoring Commissioners have held recent meetings with the chief constable and the garda commissioner, as well as extensive high-level meetings with British and Irish Government officials.
There has been speculation that their report will be published next week.