Fianna Fáil, the most successful political party in Western Europe, was facing up to its worst electoral performance in its history last night with the likelihood that it would lose a European Parliament seat in Dublin.

The party’s woes were compounded by disastrous results in local council elections and two Dublin by-elections.

Another loser last night appeared to be Declan Ganley, founder and leader of Libertas, which brought the Lisbon Treaty ratification process to a standstill when it spearheaded the No vote in last year’s Irish referendum.

Mr Ganley polled better than predicted, but his 16 per cent share in the Ireland North West constituency was not likely, after the first round of counting, to secure him its third seat.

It was also a bad night for Sinn Fein, with Mary Lou McDonald, the party’s deputy leader, on course to lose her Brussels seat.

Brian Cowen, the Taoiseach and Fianna Fáil leader, now faces demands for a general election from the main opposition party Fine Gael, which pulled comfortably ahead of its rival for the first time.

The Green Party, Fianna Fáil’s coalition government partner, fared even worse with the prospect of losing nearly all of its council seats.

All three polls had been turned into a referendum on the government’s handling of the economic crisis, a reversal in the fortunes of Ireland’s Celtic Tiger economy.

The results were so bad it was being speculated last night that the Greens might pull out of government, triggering a general election.

The Green leader John Gormley, the environment minister, said the results were “a traumatic event” for the party. He told RTE radio the party could lose 15 of its 18 local council seats. The party lost all its seats in the four local authorities around Dublin. If the results were to be repeated in a general election the Greens would lose five of their six Dail seats.

Fianna Fáil has been in power since 1997, having spent more years in government than any other West European political party. The Greens went into government for the first time after the 2007 general election.

An RTE exit poll said that Fianna Fáil would lose a European seat in Dublin. It also suggested that if a general election were to be held Fine Gael would gain 37 per cent support with Fianna Fáil and Labour on 21 per cent.

Mr Cowen described the fall in Fianna Fáil support as a poor result. “We have lost some stalwart people, good people who’ve served us well and served our communities well,” he said. “What we have to do is to reflect on all of that and rebuild for the future.”

Counting in the four European constituencies is expected to finish today.

Times Recommends

• Please help: maimed children of war want their lives back
• Unlocking the cruellest prison
• Prince Charles named in £81m court battle