Chambers Ireland said today that the "vast majority" of its members supported ratification of the Lisbon Treaty.
The organisation, which represents 13,000 businesses, said that Cork, Dublin, Galway, Limerick and Waterford Chambers are all calling for a Yes vote in June’s referendum.
Speaking at its Summit for Growth event in Druids Glen, Co Wicklow, Chambers Ireland president David Pierce said that results from its consultation of chambers was "pretty unequivocal".
"The network favours a Yes position. Chambers Ireland now fully supports
he Irish people understand that the EU has worked for us, but we can take nothing for granted. - Brian Cowen
this position."
Although no Chamber came out against the treaty, four Chambers – Carrick on Shannon, Dundalk, Newbridge, and Drogheda – opted to remain neutral on the issue.
“Ratification of the Treaty will help Ireland tackle the challenges it currently faces, help continue our global competitiveness, and will create an improved EU that works better for all,” added Mr Pierce.
Elsewhere, Taoiseach Brian Cowen said that his first priority over the next month is to secure ratification of the Lisbon Treaty.
Speaking at a meeting of the Fianna Fáil parliamentary party this afternoon, the Taoiseach said that ratification was a "defining issue" for the party.
"The Irish people understand that the EU has worked for us, but we can take nothing for granted. The Treaty’s opponents have already shown that they will use every tactic to damage it. We can only beat them if we are more active and we are relentless in explaining our message," said Mr Cowen.
"We want a Europe which reforms itself to be able to meet modern challenges like globalisation. We want an Ireland which stays at the heart of Europe. We have to reach into every community and show how the Lisbon Reform Treaty is vital. Over the next month there is no more important task for us all," he added.
The Irish Alliance for Europe, which is also campaigning for a Yes vote in the referendum, due to be held on June 12th, welcomed the fact that the three main political parties had unveiled pro-treaty campaigns over the past week.
The alliance's director, Brendan Kiely, said it would only be ratified if the public were fully informed on the issues and understand that the Treaty would lead to a more effective EU.
“The more people know about the Treaty, the basic facts as well as the more complicated arguments, the more they are likely to support it. If that is not done on a substantial level, the chances of this Treaty being passed will be significantly reduced," said Mr Kiely.
Elsewhere, Sinn Féin's agriculture spokesman, Martin Ferris, came out against one of the main parties for supporting the Treaty, however, claiming that Fine Gael's support would "impact negatively on rural Ireland.
"I find it astounding that any political party would urge rural Ireland to vote for the loss of key vetoes and a commissioner for five out of every 15 years,” said Mr Ferris.
“(The) ability for Ireland to veto decisions not in the interests of Irish farmers will be lost with the Lisbon Treaty. Article 188 of the Treaty replaces unanimity decision making on the Council of Ministers with qualified majority voting on trade decisions. This removes Ireland’s ability to veto decisions. This is a fact," he said.
Separately, former Socialist Party TD Joe Higgins claimed today that the Lisbon Treaty posed a threat to public services and would open the way to more privatisation.