Republican violence is stalling the peace process and only a rapid and definitive end to "the culture of paramilitarism" will restore partnership politics, the Taoiseach has said.
Mr Ahern, speaking in Derry yesterday, employed his bluntest language yet to insist that paramilitarism had to end and unionists had to "unequivocally embrace the principle and practice of inclusive partnership politics".
The setting was especially symbolic. Speaking alongside Mr John Hume at Magee University in Derry, the Taoiseach issued his blunt message to an audience which included Sinn Féin's chief negotiator, Mr Martin McGuinness, and party chairman, Mr Mitchel McLaughlin.
Speaking in his capacity as president of the European Council, he spoke on the EU's role in international affairs but referred extensively to Northern Ireland and what he called the "bedrock situation in the political process".
He said the people of Northern Ireland yearned for stability, peace and progress and were frustrated by the failure to "move beyond the old politics of confrontation".
Echoing much of the tone used by the British Prime Minister, Mr Tony Blair, Mr Ahern said: "We cannot have a process that is continually in crisis because there are those who will not relinquish the ways of the past."
In a reference to the alleged IRA attempts to abduct Mr Bobby Tohill in Belfast two weeks ago, he continued: "Recent events have brought into very sharp relief what was, in any event, the reality for some time.
"The continuation of paramilitary activity by the republican movement negates any prospect of achieving partnership politics in Northern Ireland."
Turning to Sinn Féin he added: "I believe the Sinn Féin leadership understand this reality and are working towards achieving that objective of ending paramilitarism."
But he warned: "The problem is that time is no longer a friend of the process." He said the Belfast Agreement had only worked sporadically and, borrowing language used by Mr Blair in a Belfast speech in October 2002, he added: "Remedying the deficits of trust and confidence that now exist requires a fast-forwarding to completion. That is the task that all parties of influence must now focus on. We all know what must be done."
The Taoiseach strongly rejected any notion that exclusion of a significant party from the political process would serve any purpose. Openly defying appeals from Mr David Trimble and from the DUP for the exclusion of Sinn Féin, he said: "Some parties seem to believe that a policy of exclusion is the answer. It is my belief that any such policy would not be workable."
Speaking afterwards, Mr Ahern told The Irish Times: "We had penalties before against parties - Sinn Féin and the Ulster Democratic Party out. What did we do after that? We brought them back in again."
He denied the Government's attitude towards Sinn Féin had hardened.
"There is no change in our policy, and won't be."
Asked if he privately considered a deadline for so-called acts of completion by republicans, he answered: "We haven't reached that time yet."