Dublin  - The no side has surged ahead a week before Ireland holds a referendum on the European Union's Lisbon Treaty, a poll showed Friday.

The TNS/mrbi survey of 1,000 voters carried by the Irish Times showed opponents of the treaty 5 per cent ahead of those in favour. All polls up till now had shown the yes side in the lead.

The no side now stands at 35 per cent, up 17 per cent since three weeks ago, while the yes side has lost five points to 30 per cent. Some 35 per cent of voters still haven't made up their minds.

Ireland votes on the treaty on June 12, the only one of 27 EU member states to hold a public referendum on the treaty aimed at simplifying decision-making in the bloc.

An Irish no would mean the treaty, a replacement for the failed EU constitution rejected by French and Dutch voters, could not go into effect.

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.

All the major Irish political parties have been campaigning for a yes vote. (dpa)