The Government must now demand the renegotiation of the Lisbon treaty, victorious No campaigners insisted today.
Sinn Féin, the only main political party to oppose ratification, said Taoiseach Brian Cowen must listen to the electorate and raise their concerns about the EU reform proposals with other European leaders.
Voters rejected the treaty 53.4% to 46.6% in a referendum this week.
Sinn Féin MEP Mary Lou McDonald has called for a meeting with Mr Cowen to discuss the way ahead in the wake of the poll result.
"Yesterday the Irish people gave the Government a clear and strong mandate to renegotiate the Lisbon Treaty," she said.
"At his first European Council meeting as Taoiseach next week Brian Cowen should set out in clear and unambiguous terms the concerns raised by the Irish people and the need for these concerns to be properly addressed.
"Throughout this referendum campaign a number of specific issues came up over and over again - Ireland's loss of power in Europe including the loss of a permanent Commissioner, neutrality, the race to the bottom in wages and conditions and the opening of key public services to competition.
"Many of these same concerns were raised by the people of France and The Netherlands when they rejected an almost identical package in 2005. And they have been raised by many political voices across the EU over the last twelve months.
"Now is the time for calm voices. Ireland's place in the EU is secure. Suggestions from a small number of EU leaders that they can blindly continue on with the Lisbon Treaty are not just undemocratic but also untrue. The Lisbon Treaty needs the support of all member states to come into effect.
"The people have been asked on three occasions their views on the content of this Treaty and on three occasions it has been rejected.
"European leaders now have an opportunity to listen and to address these genuine concerns.
"There is also a responsibility on all of us who believe that a better deal is possible, to support and assist the Government in their task.
"Sinn Féin wants to be constructive. We will be seeking a meeting with the Taoiseach in the coming days to discuss with him the issues, which we believe can be addressed in a renegotiated Treaty."