The economic welfare of this State would be put at risk by another rejection of the Nice Treaty, the Irish Alliance for Europe has claimed.
In a meeting in Dublin today, the group said a No vote would diminish "our attractiveness as a location for Foreign Direct Investment."
"We will be seen to have lost out commitment to European integration and to have blocked the historic re-unification of the European family," it said.
The Alliance said a No vote will also curtail our access to the fast-growing markets of Central and Eastern Europe as it would invoke an "understandable hostility from candidate countries".
Professor Colm Kearney of International Business at Trinity College said: "The anti-Nice lobby argues that enlargement will hurt Ireland economically because capital will move east and labour will move west."
Professor Kearney said: "This is a gross oversimplification. If we vote No, it will surely drive capital eastward. The best way to protect our jobs and prosperity is to remain fully engaged in Europe."
Human resource director of CRH, Mr Jack Golden, said citizens in candidate countries were "bewildered and dejected when Ireland said No to Nice last year."
Mr Golden said: "If we close the door on them a second time, they will see our rejection of their legitimate aspirations as self-centred and selfish."
"The consequences of a No vote Ireland - a small, open economy vitally dependent on developing trade and investment in an enlarged EU market - will be immediate and adverse," he said.
Mr Sean Melly of eTEL group said EU enlargement would spur a deregulation of the telecom sectors in candidate countries which would benefit many Irish firms associated with the industry.
