Ireland holds the fate of the European Union's Lisbon Treaty, voting on whether to ratify the treaty aimed at reforming the EU institutions. Ireland is the only country in the EU that is holding a referendum on the ratification of the accord.

The vote is crucial given the recently increased anti-European sentiment in Ireland. On June 9, Reuters quoted a Red C opinion poll published in the Sunday Business Post newspaper, according to which 39 per cent of Irish voters intended to vote against the ratification, while 42 per cent meant to vote in favour.

According to the agency, however, other polls indicated those who were against the ratification were narrowing the gap.

The Lisbon treaty can only go into force if all 27 EU member states ratify it. Should Ireland reject it, it would mean a new political crisis for the bloc, given that the treaty itself is a re-worked version of the EU constitution, rejected by French and Dutch voters in 2005.

So far 18 EU members have ratified it, the lastest being the parliaments of Estonia, Finland and Greece on June 11. Bulgaria's Parliament ratified the treaty on March 21.