Ireland's largest trade union has abandoned its "once in a century" hope of a left-wing government just days before voters go to the polls.
Siptu has conceded there is no "feasible prospect" for a coalition of leftist parties and independents forming a coalition after next week's general election.
The declaration comes a year after the union's president Jack O'Connor claimed the country was at an extraordinary juncture in history which would allow the massive political swing for the first time in the state's history.
But in a statement to the union's magazine Liberty, Siptu's ruling executive urged its 200,000 members to back Labour as the only way of balancing another right-wing led government.
"Obviously, we would prefer a left of centre government," it said.
"However, there is no feasible prospect that it can come about in this forthcoming election."
The union's national executive said Fine Gael could win a majority with just over a third (35%) of first preference votes because the opposition is so splintered.
"Worse still, they may fall just short of it, requiring them to rely on the support of Renua and a handful of right-wing Independents," it said.
Siptu also claims a Fine Gael and Fianna Fail coalition - which has been ruled out in a televised debate by Taoiseach Enda Kenny - would be the most right-wing government in the history of the state.
It ruled out any prospect of a Fianna Fail and Sinn Fein alliance, even supported by a number of Independents, because of the need for a strict transfer voting pact.
The union said a future left-leaning government would require parties making compromises and facing up to difficult issues.
"However, as far as this forthcoming election is concerned, the only way of depriving the right of a monopoly of power and thus protecting the basic interests of working people and their families is if Labour wins enough seats to balance them in government," it added.
Despite the prediction of a possible Fine Gael majority, party leader Mr Kenny appeared to rule out such a scenario, claiming he would prefer a coalition rather than a single-party government.
As the latest in a series of opinion polls showed another slide in support for the senior coalition partners, the Taoiseach insisted he remained optimistic and did not take notice of pollsters.
"This was always going to be a dogfight," he said.
"Did anyone think this was going to be a cakewalk or a doddle? I didn't."
Health Minister Leo Varadkar also acknowledged that another drop in the polls, putting Fine Gael at 26%, signalled his party may not be the largest after February 26.
"It is an election, the election is competitive," he said.
"I think certainly it was never the case in Fine Gael but there was an assumption by people in the media that no matter what would happen, Fine Gael would emerge as the largest party. That might not be the case."
Jobs Minister Richard Bruton said there is "a real danger that Irish voters will sleepwalk into making a decision that they will regret" next week.
Sinn Fein deputy leader Mary Lou McDonald accused Siptu of "a betrayal of working people" over its call for a strong Labour vote.
"Before a vote has even been cast, the Siptu national executive has thrown in the towel and backed a Fine Gael led government and its plans to give massive tax breaks to the wealthiest in our society," she said.
"This is a betrayal of working people."
Ms McDonald claimed an opportunity remained to elect a progressive government.
"Siptu would serve its members in a much better fashion if it would throw its weight behind this effort," she added.
"It must realise that the Labour Party has abandoned the 'left of centre' space that it speaks of and that another Fine Gael led government can only mean more chaos for the people Siptu represents."