The Labour Party's days in Government are numbered unless it pursues a different agenda, grassroot members warned.
More than 60 members of the coalition party met in Dublin to put pressure on the leadership to implement more Labour policies in Government.
The Campaign for Labour Policies wants Tanaiste Eamon Gilmore and his minister to stand up to Fine Gael and tax the wealthy.
Councillor Cian O'Callaghan said: "A sharp wake-up call has been issued to the Labour Party in recent weeks with the resignation of Nessa Childers MEP, the poor by-election result and the collapse in Labour support in the polls.
"This is the last chance for the Labour Party to assert its relevance in Irish politics as a vehicle for progressive change.
"If the Labour Party does not pursue a broad progressive social democratic agenda in Government its days are without doubt numbered," the Mayor of Fingal added.
MEP Nessa Childers resigned from the parliamentary party amid claims she could no longer support a Government that was hurting the public.
While she will remain in the Labour Party, she joined fellow members in opposition to campaign for Labour policies.
Her resignation came a week after the party was hammered in the Meath East by-election, when candidate Eoin Holmes polled fifth with just 5% of votes.
Five other TDs have quit the parliamentary party since Labour took office in 2011 - including former junior minister Roisin Shortall, Colm Keaveney, Tommy Broughan, Patrick Nulty and Willie Penrose, who intends to reapply for membership in the near future.