The country's largest union has said it acknowledges there is "no feasible prospect" of a left-of-centre government emerging from the forthcoming election.
However SIPTU has urged members to vote Labour, but to enhance the prospects of a left-leaning government by giving preferences to candidates standing on other left-wing platforms.
The call comes in a statement from the union's National Executive, published in the union's magazine, Liberty.
The executive says the only way to protect public services and working people - and to deprive the right of a monopoly - is if Labour wins enough seats to balance the right in government.
However, the union leadership acknowledges that while SIPTU would obviously prefer a left-of-centre government, there is "no feasible prospect" that it can come about in this election.
The National Executive says that the union needs to work towards a left-of-centre government in Ireland, but that it will require cooperation by all those who believe they are on the left - and that in turn means facing up to difficult issues and compromise.
It says the lesson of the recession is that they must never allow the right in Ireland to obtain a monopoly on power again - but warns that that is the prospect which now threatens as the outcome of the 2016 election.
It dismisses the possibility of a Fine Gael-Fianna Fáil coalition as potentially the most right-wing government in the history of the State - involving a combination of those who introduced the "ruinous" bank guarantee and those who "most enthusiastically" supported it.
It notes Fine Gael can actually win a majority with just 35% of the first preference vote because the opposition is so splintered.
It says that worse still, Fine Gael may fall just short of it, requiring it to rely on the support of Renua and a handful of right-wing Independents.
It says a Fianna Fáil/Sinn Féin alliance supported by independents would require a very disciplined transfer voting pact which is "not in prospect".
