United Left Alliance TDs will campaign in the Dáil against stealth taxes including water charges and property taxes if they were elected, Socialist Party MEP Joe Higgins said.
He said "mainstream media commentators" were predicting that the alliance could win at least six seats in the next Dáil and that would mean "the possibility of a very significant new development in Irish politics".
If they had a "good result" in the general election they would establish a new political party of the left, he said.
Mr Higgins was speaking as some of the alliance's 20 candidates held their final rally at the statue of union leader James Larkin on O'Connell Street in Dublin.
People Before Profit councillor Joan Collins said she knew she'd be "battling for the last seat in Dublin South Central" and the choice was between herself and Fianna Fáil's Michael Mulcahy.
"It would be absolutely brilliant to be in the Dáil with six or seven other TDs who will provide principled opposition," she said.
Cllr Richard Boyd Barrett of People Before Profit said he believed the alliance could win between six and 10 seats. A candidate in Dún Laoghaire, he said they planned to provide "a real opposition to the agenda of cuts".
The alliance planned to campaign against stealth taxes including water charges and property taxes, which he claimed the new coalition would begin to implement during its term of office. "These are just new ways of robbing people to pay off the speculators' debts," Mr Higgins said. "With a good result the United Left Alliance will be in position to launch a new political movement of the left, a new political party of the left that is an alternative to the entire establishment".
He said the six potential seats for the alliance were himself in Dublin West; Cllr Mick Barry in Cork North Central; Cllr Boyd Barrett in Dún Laoghaire; Cllr Joan Collins in Dublin South Central; former TD Seamus Healy of the Unemployed Action Group in Tipperary South and the Socialist Party's Clare Daly in Dublin North.