Mr Pat Rabbitte has signalled moves to form a platform with the other Opposition parties by describing the June elections as a "vital stepping stone" on the path to forming an alternative government.
The Labour leader's remarks to a party meeting in Killarney follow calls from the Fine Gael leader, Mr Enda Kenny, for a "coalition of the caring" to challenge the Government.
With Labour, Fine Gael and the Greens signing up for three joint Dáil motions in recent weeks, the Opposition is laying the groundwork for closer co-operation and a possible pre-election pact.
Mr Rabbitte, who has in the past ruled out entering government with Fianna Fáil, said the Government was willing to do whatever it takes to remain in office. "One of the consequences of their lack of care is that as we have become richer we have become more unequal."
He described the local and European election campaigns as "only part of the work" for Labour.
"They are a vital stepping stone on the road to building a decent and credible alternative to the dreadful Government we have in Ireland."
While he did not directly refer in his script to the other Opposition parties, he said Fianna Fáil and the PDs had redistributed wealth upwards.
Labour had a duty to build an alternative to the Government, he said, adding that the people of Ireland were disillusioned with politics.
"The widespread perception exists, and it is damaging to all forms of democratic politics, that all politicians are the same, that we can all be tarred with the same brush.
"I intend to spend the next couple of years proving that nothing could be further from the truth."
