Fianna Fáil Leader Micheál Martin has accused the Government of knowingly putting patients' safety at risk after it "cooked the books" on the health budget last year.
Mr Martin said correspondence from the Health Service Executive and the former minister for health James Reilly proves that spending cuts planned last year would not have safeguarded patients' safety.
He was speaking at his party's two-day pre-Dáil meeting in Roscommon town.
Mr Martin said it is clear the Government has lived a lie on its health reform plan, which he said was a sham that was never going to happen.
He said the Government had planned to take hundreds of thousands of medical cards from people until it changed its approach after the Local Elections.
On his own party's standing in the opinion polls, he said Fianna Fáil emerged as the biggest party in local government after last May's elections.
Mr Martin said his party wanted to contribute and to be in Government after the next election.
He said the election outcome would determine how this could happen, but he said Fine Gael would not make comfortable bedfellows for his party.
The gathering is set to focus on the economy and there will also be a discussion on problems facing beef farmers.
The party's spokesperson on Enterprise and Jobs, Dara Calleary said many people are not experiencing any economic recovery.
Alan Aherne, the head of economics at NUI Galway and former adviser to the late Brian Lenihan, is to address TDs and Senators this evening.