A SECOND Lisbon referendum vote next year is being seen by senior political sources as a de-facto ballot on Ireland's future in the European Union.


The main political parties are nervous about the prospect of a second poll. Another defeat would not just result in Ireland being sidelined in the EU but would almost certainly precipitate a general election.


Although both the 'yes' and 'no' camps have insisted publicly the rejection of the Lisbon Treaty 10 days ago was not an anti-EU vote, privately politicians admit that another 'no' vote in a second Lisbon referendum would end Ireland's status as a core EU member.


"There is no legal mechanism in place for a country to leave the EU, but a way will be found to do it [in the event of a second Lisbon defeat]," one source said.


The implications of a 'no' vote make it inevitable, political sources say, that 'Lisbon II' will boil down to: "Are we in, or are we out?"


"It's virtually inevitable that the referendum will be fought along those lines," said one senior political source.


And it is also accepted across the main political parties that it would be impossible for the government to continue in the event of another referendum defeat.


"The Taoiseach would have to go to the country," another source said. The ensuing general election campaign would be fought on one issue: Ireland's future in the EU.


A week ago, all the main political parties were ruling out a second referendum, because of the relatively high turnout and the emphatic nature of the 'no' vote. However, attitudes have changed dramatically since Ireland's EU partners have made it clear renegotiation of the Lisbon treaty is not an option.


A government source yesterday stressed the Taoiseach had resisted pressure to be tied down on what the next move should be and said no decision had been made on a referendum or any other option. However, Axel Poniatowski, an official spokesman for French president Nicolas Sarkozy said yesteray there was no "other choice" to a second referendum.


This was echoed by a senior source in one of the opposition parties here who said: "Is there now a momentum for a referendum? Yes, there is."


There is hope that the government will be able to make some progress in negotiations over the coming months – most notably on the issue of a permanent commissioner – to make a second referendum more saleable to the Irish public. But there is also an acceptance that any changes are likely to be marginal.


And there is some concern, particularly given the hugely difficult economic climate, about the prospects of getting Lisbon II passed. Against that, some politicians believe the stark nature of the choice on offer to voters should ensure a 'yes' vote.