The DUP leader, the Rev Ian Paisley, has rounded on the Taoiseach for questioning the party's commitment to power-sharing.
Dr Paisley said the DUP would not sign up for any "ragbag" deal. He said it was outrageous that Mr Ahern was "now in the business of lecturing unionists to admit Sinn Féin/IRA into the government of Northern Ireland at a time when his own party refuses to countenance Sinn Féin in power in the Republic".
"Mr Ahern would be better spending his time ensuring that Sinn Féin/IRA decommission all of its weapons in a way that satisfies everyone and brings to an end all of its activities," he said.
Dr Paisley said Mr Ahern's comments indicated "bad faith" and that it was time the Government "faced up to its responsibilities and stood shoulder to shoulder with those who are demanding an end to terrorist and criminal activity".
"We are in the business of getting a fair deal for Northern Ireland, but Mr Ahern and his officials had better realise that we will not be settling for any ragbag deal just because he says we are facing a deadline," he added.
"The DUP will not be bullied, and I will not be dictated to by those who would want us to settle for much less than our election commitments. The Irish Government must remember and realise that unionists will not be lectured about the internal workings of Northern Ireland. These are not issues for Dublin. There are just two words for Mr Ahern - heal thyself!"