Fine Gael has accused the Taoiseach, Mr Ahern, of hypocrisy over terrorism after pointing out that a Bill to introduce new counter-terrorism measures has been delayed in the Dáil since 2002.
The attack on the Taoiseach by the Fine Gael leader, Mr Enda Kenny, came ahead of a summit of EU justice and home affairs ministers to discuss the bomb attacks in Madrid last week.
It followed Mr Ahern's commitment in Washington on St Patrick's Day to put forward a declaration on counter-terrorism measures that can be introduced immediately.
Mr Kenny said the Criminal Justice (Terrorist Offences) Bill of 2002 "lies gathering dust" in the Dáil after a Second Stage debate.
The Bill seeks to implement an EU framework decision on combating terrorism, and allows the inclusion in Irish law of an international convention on the taking of hostages.
It also includes an international convention on the suppression of terrorist bombings, and on the suppression and financing of terrorism.
Mr Kenny said such issues needed to be addressed urgently. "Sixteen months later, the Bill has made no further progress. Responsibility for this lies fairly and squarely at the door of this Government.
"It begs the question as to why the Taoiseach is calling for EU-wide support for action on terrorism when he won't even implement his own legislation on this very subject."
A spokeswoman for the Department of Justice said the Bill was "only one of a number of proposals" before the Oireachtas.
She said the Minister for Justice, Mr McDowell, was considering amendments following the Second Stage debate, and taking into account observations from the Human Rights Commission.
"It is one of the Minister's legislative priorities, and he hopes that he will have the co-operation of all parties to have it enacted as soon as possible."