Prime Minister Brian Cowen warned yesterday that recession-mired Ireland's recovery depends on it backing the EU's Lisbon Treaty, as voting got under way in a crunch second referendum.

Another No vote would damage Irish hopes of reversing its sharp recession and would plunge the EU into "extraordinary uncertainty", Mr Cowen said.

Irish voters dealt the EU a stunning blow in the first referendum last June, but opinion polls indicate they will reverse that decision. The latest survey on Sunday gave the Yes campaign 55 per cent, against 27 per cent for the No camp.

The premier's warning came as voting started on five Atlantic Ocean islands which cast their ballots early in case bad weather holds up transporting the ballot boxes to the Irish mainland, which votes tomorrow.

The first eligible voters in the referendum are some 750 citizens on five islands off County Donegal in northwest Ireland. The largest island, Arranmore, has more than 500 residents while the smallest, Inishfree, has only seven.