The Dáil has voted for the Government motion on Iraq today by 77 votes to 60.
It was always expected that the Government's motion - which included allowing the US military continued use of Irish airspace and landing facilities - would be passed, despite backbench rumblings from within the Government parties.
Labour Party leader Mr Pat Rabbitte said earlier when the motion was adopted, "Ireland will no longer be a militarily neutral country".
Opposition parties looked for more than the six hours allocated to debate the issue when the specially recalled Dáil met this morning. But the Taoiseach, under pressure of time because of an EU meeting later today in Brussels, said the house had debated Iraq a number of times since January and that there had also been several leaders' questions.
"The six hours today should allow representatives of all political parties in this House to put their party's position," Mr Ahern said.
The Fine Gael leader Mr Enda Kenny said: "You cannot uphold the primacy and legitimacy of the UN and agree to provide facilities in a war it has not mandated".
He also said the Taoiseach's assertion that "Ireland would be the only country in the free world not to offer its assistance in this war" is wrong.
"Countries such as Austria, Switzerland, Finland and Sweden are showing their opposition to this war by denying the use of facilities. Moreover, countries such as Germany who allow troops move through their territory are NATO-allied. We have no such alliance," he said.
He also warned that Ireland may become a terrorist target because of the help the Government was offering the US war effort.
Labour's Mr Rabbitte said an artificial distinction had been made between the Government position on the war and the use of Shannon. "As a direct consequence, this is the first government in the history of this State to decide to put aside the foreign policy and international relations precepts, propositions and principles enshrined in the Constitution".
He also derided the argument that Ireland's economic interest could be damaged by withdrawing Shannon. He referred to the importance of the "special" relationship Ireland has with the United States and said "it is spurious to suggest that US multinational investment in Ireland would flee if our Government had the courage to assert our traditional neutrality in the face of an unsanctioned war".
He reminded the Dáil: "There is hardly a modern bus or train, a railway station, tunnel or motorway that is not assisted by Europe . . . hospitals, local amenities, libraries, water and sewerage services, initiatives in education, all have been facilitated by EU investment, by enormous transfers of resources from the likes of Germany and the other net contributors to the EU budget.
Green Party Leader, Mr Trevor Sargent said the Government's position over the use of Shannon was in breach of the UN Charter and the Hague Convention.
He also challenged the Taoiseach to produce the Attorney General's legal opinion on the matter: "We have heard plenty of the Government's political rhetoric on the continued use of Shannon but no sound legal opinion".
Sinn Féin's leader in the Dáil Mr Caoimhghín Ó Caoláin said the Government had not put forward any "argument of principle ... to justify the continued provision ofShannon [by] the US military".
He was aprticularly critical of the Taoiseach's reference to the US of Shannon during the Vietnam war for justifying its continued use by the US military.
"Does the Taoiseach believe that Ireland's facilitation of the US military machine during the Vietnam war, whenchemical weapons such as agent orange and napalm were unleashed on the civilian population of that country, was right or wrong?
"It is conservatively estimated that over 2 million people died in that war. This is hardly a glorious precedent to cite in again justifying Ireland's facilitation of the USmilitary on route to war."