Fine Gael and Fianna Fail have been accused of treason and sabotage over plans to suspend water charges in order to clear the path for a minority government.
Outgoing Environment Minister Alan Kelly launched the withering attack on his former cabinet colleagues and opposition benches as the contentious issue looks set to make or break power for acting Taoiseach Enda Kenny.
Fine Gael confirmed they want a nine month suspension of charges to let a special commission examine Irish Water's charging regime and its much-maligned funding model.
Fianna Fail leader Micheal Martin insisted his party w as committed to the suspension of charges until the next election.
The responses came after Mr Kelly used one of his final speeches as a minister to fire broadsides at his opponents and defend the idea of asking people to pay for water from an environmental, conservation, common sense and economic point of view.
The Labour deputy leader said a deal to suspend charges or abolish Irish Water as a utility would throw Ireland back to the 19th century.
"I believe we are about to witness the triumph of mediocrity over modernism, of short-termism over common sense and immaturity over innovation," Mr Kelly said.
"If the scrapping of Irish Water goes ahead, let's call this what it is, political, economic and environmental sabotage."
Mr Kelly claimed the lifting of charges would lead to water shortages in Dublin in the future and continue the pumping of 20,000 tonnes of sewage into Cork harbour every day.
And he likened the reported deal on a minority government to the abolition of household rates in 1977 by Fianna Fail which ultimately created a massive hole in the country's finances and led to crippling income tax rates of up to 60% in the 1980s.
"We risk repeating that mistake again. Every other EU country has some type of domestic charge on water," he said.
Negotiations between Fine Gael and Fianna Fail continued while the Taoiseach put his case to parliamentary party members.
They also include an option to refund about two million payments for people who paid Irish Water bills.
Since its inception in 2013, Irish Water has overseen the building of 34 new treatment plants - 26 for sewage and eight for drinking supplies - and fixed or replaced 454km of pipes.
Some 17,300 people in Roscommon have also seen boil water notices lifted.
Mr Kelly also claimed 34 million litres of water - enough to supply Co Wicklow for one day - which was being lost through leaks was now staying in the supplies every day.
The outgoing minister also claimed Ireland could be facing millions in fines from Europe if water charges were abandoned.
A commitment to them was made by the Fianna Fail-led government in 2010 when it signed up to the Water Framework Directive as the country went bankrupt.
Mr Kelly also said water conservation was a necessity in tackling climate change.
"A former politician once stood in this house and accused Fianna Fail of economic treason - today I believe Fianna Fail are guilty of environmental treason and the Labour party stands behind the important public service of water provision," he said.
"Politics is failing the people of the country again. Utopian populism is winning again. It's Groundhog day. We will regret it, just as we did in '77."
Sinn Fein leader Gerry Adams backed the idea of TDs having the power to determine the future of Irish Water, claiming there were now a majority of politicians in Leinster House against the regime.
"Fianna Fail's manifesto, not once, but in three separate sections clearly calls for the abolition of Irish Water and the scrapping of water charges. It says nothing about the suspension of charges, or maintaining the mechanism for charging on the statute books," he said.
Fianna Fail leader Mr Martin said: "This is very far from being the single most important issue facing our country, however it is important and the handling of it in recent years represents a dramatic public policy fiasco."
But he added: "The policy we are committed to remains a scrapping of the commercial state firm, no charges for at least the duration of this Dail and a major national investment programme in developing this vital public service," he said.
Simon Coveney, Cabinet minister and Fine Gael negotiator, rejected allegations from some opposition figures that Irish Water was destined to be sold off by the state.
"The accusations from some of a secret agenda of privatisation is completely bogus and untrue," he said.