The Fine Gael leader, Mr Enda Kenny, has condemned remarks by the Taoiseach suggesting the IRA killers of Det Garda Jerry McCabe would have to be released as part of a final peace deal.
"The people can no longer believe a word this Taoiseach tells them," Mr Kenny said.
"He has been completely dishonest in his dealings with the people in relation to the release of the killers of Jerry McCabe and so many other matters.
"He says one thing in public and then makes secret arrangements with the Provisional IRA without any consultation with Dáil Éireann.
"Are we now to understand from the Taoiseach's comments that a lasting peace on the island hinges on the release of the killers of Detective Jerry McCabe?" Mr Kenny asked.
In February 1999, the Special Criminal Court sentenced four men to jail terms ranging from 11 to 14 years for the manslaughter of Det Garda McCabe.
Pearse McCauley, from Strabane, Co Tyrone; Jeremiah Sheehy, of Abbey Park, Rathkeale, Co Limerick; Michael O'Neill, of Lisheen Park, Patrickswell; and Kevin Walsh, also of Lisheen Park, Patrickswell, Co Limerick, are being held in Castlereagh Prison.
At the launch of Fianna Fáil's local election campaign yesterday in Dublin, Mr Ahern said Sinn Féin had been consistent in arguing that the release of the four men was essential to any final peace deal.
"They keep it on the agenda, in fairness to them, at all times. I don't think that I have had a meeting with them where they have not touched on this issue.
"I am long enough dealing with them. I know when they are telling the total truth and when they are negotiating," he told The Irish Times.
Mr Ahern said the Government had responded "that we will consider it, but only in the context of a final agreement".
Under Paragraph 13 of the Anglo-Irish Joint Declaration agreed last year, the two governments demanded a complete end to paramilitary activity.
Mr Ahern said yesterday: "If I could go to the Irish people and say, 'I am in the final negotiations and that I believe that Paragraph 13 is finally signed off after 30 years of what the people on this island have suffered and one of the issues is that I have to release the remaining prisoners and that I am asking people to understand that', I would go and explain that to the public.
"I would think that that would be a reasonable thing for me to do but, of course, I would take into account the sensitivities of the widow and the family. I wouldn't just do it off the top of my head."