Irish voters were warned by Brian Cowen, their prime minister, on Tuesday not to think they could extract a better deal from their European Union partners by rejecting the Lisbon treaty in Thursday’s referendum.

“To those who say ‘Go back and start again’, I have a very clear response,” said Mr Cowen. “This is an excellent treaty. It was shaped by Ireland more than any previous European document in the 35 years of our participation in the great European project.”