In a strongly pro-European speech, the Taoiseach said last night he would "defy anybody to say that membership has not been good for Ireland".
Speaking in Ballymun, Dublin, at a local meeting organised by the National Forum on Europe, he said the alternative would be "to face the world alone".
Describing the Nice Treaty as a "modest step", the Taoiseach argued that: "In any organisation, proposing to virtually double its size, changes in the manner of doing business are necessary. It is as true of a community organisation or sports club as it is of the European Union." Outlining the advantages of EU membership he said, "We have punched way above our weight for a peripheral member-state of just four million people.
"We are respected not just by the current members. Those seeking to join look to us as a role model."
"There was no other realistic choice: "I ask you to think of the alternative.
"It would be to face the world alone. Would that be in any member state's national interest? Would it be in ours? I don't believe so."
He said the forum's regional meetings had given the people of Ireland a chance to have their voices heard "in this vital debate for the future of our country". "The benefits of EU membership are all around us. Only a decade ago unemployment stood at 18 per cent. Today it is down to 4 per cent and our membership of the EU has been central to job creation.
"Today our people, if they choose, can work in any country in the Union not because they have to but because they want to. All of us remember when the opposite was the case."
The EU member-states had together created a single market for our exports. "It is the huge growth in Irish exports which has led to our low unemployment rate. Enlargement of the Union will make that market even bigger and Irish companies are already bedding down in those countries which have applied to join.
"That said, the EU is by no means perfect. It can be bureaucratic. It can be slow to act. It can feel remote. But it is a voluntary union.
"Nobody forced us to join. Nobody is forcing us to stay. And I defy anybody to say that membership has not been good for Ireland." The EU was the "best effort" to date at creating a framework for peace and prosperity throughout the European continent. That was why 12 new states wanted to join. "The EU has been built up slowly but surely. At each stage all the member-states have had to agree to its further progress. That has been the case with the euro, although three member-states have yet to adopt it. It was the case with the common approach to the single market and it is the same approach to a more co-ordinated policy for peacekeeping. The Nice Treaty was, in my view, and that of the Government, a further modest step in building our common approach."
The "key message" he wanted to give was that everyone should be proud of Ireland's contribution to the EU. "We should engage with Europe. We should be confident of our ability to shape the agenda as we have done for the last three decades.
"We should be confident that Europe is no threat to our national culture or traditions.
"We should be confident that a strong Ireland in a strong Europe is the best way forward for our people," Mr Ahern said.