Voting was well under way in Ireland Thursday in a referendum on the Lisbon Treaty designed to streamline the running of the European Union, with the risk of a rejection setting nerves jangling across the EU, according to dpa. Polls opened at 7 am (0600 GMT) and were due to close at 10 pm, but a low turnout as reported by national broadcaster RTE in the early afternoon was expected to pick up as people voted on their way home from work. Ireland's Prime Minister Brian Cowen, who is staking his political future on a yes vote, cast his vote in the midlands town of Tullamore at 10 am (0900 GMT). Opposition Fine Gael leader Enda Kenny, who also campaigned for a yes vote, voted in Castlebar, Co Mayo, in the west of Ireland. Declan Ganley, the founder of Libertas, which has been leading the no campaign, was also in the west of Ireland to vote. Turnout ranged between 20 per cent in Clonmel to just 4 per cent in Roscommon, RTE reported. Just over 3 million Irish voters were called to the polls to vote on the treaty. Polling is taking place in 43 constituencies. Ireland is the only one of 27 EU member states to hold a public referendum on the treaty, and it is unclear what will happen if the country votes no. RTE reported that the other 26 member states could move forward with Lisbon, leaving Ireland to negotiate with them as a group, but supporters of the treaty have said it will collapse with a no vote, while the treaty's opponents say it could be renegotiated and then Ireland would vote again. To date, 18 national parliaments have voted to ratify the treaty, including Germany where the president must now sign the treaty to ratify it formally. On Wednesday alone, the Finnish, Estonian and Greek parliaments ratified the treaty. The lower house in the Netherlands has approved the treaty, but the upper house has yet to vote on it. The latest opinion polls have shown the result of the referendum balanced on a knife-edge. There was a surge in support just ahead of the vote for the no campaign to 35-39 per cent, while those backing yes were down to between 30-42 per cent, leaving around one-third of the 3.1-million electorate undecided. All the major Irish political parties have been campaigning for a yes vote. The no campaign has argued that the treaty threatens Ireland's neutrality, influence in Europe and advantageous corporate tax regime. Irish voters have caused headaches for the EU in the past, rejecting the Nice Treaty in 2001 before approving it in a second referendum a year later. Vote counting begins Friday at 9 am with official results expected to be announced by late afternoon.