The Social Democrats say they have lodged a formal complaint with RTÉ over their exclusion from the final televised leaders' debate before the general election.
Tomorrow night's Prime Time debate will feature Enda Kenny, Joan Burton, Micheál Martin and Gerry Adams.
However, a number of smaller parties and independents have criticised the state broadcaster for not including them.
The Social Democrats say they have now lodged a formal complaint with the broadcaster's Director General, claiming their exclusion is "essentially censorship".
The party's co-leader Stephen Donnelly said, "we're trying to get a message out on a fraction of the resources available. When the State broadcaster is essentially engaged in censorship of four of the eight political parties three days before the debate, it makes it very difficult.
"Personally, I think the Irish people would prefer as full and frank a debate as possible, as opposed to a debate of the establishment from the establishment," he added.
The People Before Profit group has also criticised RTÉ ahead of the debate for not including Richard Boyd Barrett, despite his appearance in last week's debate.
Spokesperson Kieran Allen said, "this debate does not represent a huge number of people who, according to consistent opinion polls, will not be voting for the main parties. We feel that Richard Boyd Barrett should be included in this debate".
The Renua leader Lucinda Creighton earlier said she has written to Ireland's three TV stations asking to be included in another leaders' debate.
Last week, the Green Party lost its High Court bid to be included in the second general election leaders' debate on RTÉ.
