A government led by Fine Gael and Fianna Fail does not represent the change that people voted for, Sinn Fein leader Mary Lou McDonald has claimed.
Ms McDonald set out her stall as the de facto leader of the opposition as members of Fine Gael, Fianna Fail and the Green Party prepare to decide whether or not to approve the programme for government.
The Sinn Fein leader claimed the agreement was an attempt to deny change, protect the status quo and "to continue with the same broken politics that has so badly failed workers and families".
She argued the agreement was not the only deal possible and said the "chance to form a government of change is real".
Ms McDonald said that Taoiseach Leo Varadkar and Fianna Fail leader Micheal Martin set about to exclude Sinn Fein and "in doing so they excluded the demand for change coming from the people."
"Grassroots members of the Green Party know this. Grassroots members of Fianna Fail also know this," she added.
Both Mr Varadkar and Mr Martin ruled out going into government with Sinn Fein before the election, citing differences in economic policies and the party's association with the Provisional IRA.
After the election, Mr Martin told the Dail he could not go into coalition with Sinn Fein because of its "efforts to legitimise a murderous sectarian campaign".
Dublin Central TD Ms McDonald responded at the time saying she "did not care" what he thinks about her party.
Speaking ahead of a potential Fine Gael/Fianna Fail/Green government being formed, Ms McDonald said "no matter what happens, workers and families must not be the ones to shoulder the pain of the economic crisis" and warned: "There can be no return to austerity."
She added people are "impatient for change" and Sinn Fein has the policies to "deliver a fresh start", listing proposals to set the pension age at 65, create a single-tier health service and provide affordable housing.
"We won't let any government turn their face against these solutions that people so badly need," she said.
"Sinn Fein won't allow Fianna Fail and Fine Gael to waste the potential, the possibilities and the aspirations of our people.
"There is a better and a fairer way and that means putting people and communities first.
"Sinn Fein will defend the change the people voted for."
Elsewhere, Rise TD Paul Murphy claimed that the programme for government was a "trap" for the Green Party.
He argued that it contains "vague talk of change to lure the Greens in to be a green mudguard for austerity".
The Dublin South-West TD urged the Green Party's grassroots members to reject the deal.
Solidarity TD Mick Barry criticised housing proposals in the document, saying: "Building 50,000 social homes over five years is not nearly enough to address the housing crisis."