Taoiseach Enda Kenny has warned there will be no reform of the Seanad if the public votes to keep it.
In a last-ditch bid for support for the abolition of the upper house, he said the choice for voters was simple: scrap it or retain it.
"The Seanad is an ineffective, powerless body," Mr Kenny said.
"It costs 20 million euro a year. It is undemocratic. It is minority representative. It is not possible to reform this body."
The Taoiseach was joined by Tanaiste Eamon Gilmore in a last campaign push, urging the public to vote Yes on Friday.
Mr Gilmore said abolishing the Seanad would lead to true political reform - changes he and the Taoiseach had planned to discuss with the opposition parties.
He said the fate of the second chamber now lies in the hands of the public, and that while he believes Ireland should have only one parliamentary body, he would ultimately accept their decision.
"It is a decision for the people to make and whatever decision the people make, that is decisive," Mr Gilmore added.
"That is how our Constitution is decided. The Constitution belongs to the people."
Opponents to the Government's campaign to abolish the chamber have argued it should be retained and reformed - a move the Taoiseach has insisted is not possible.
As the longest-serving member of the Dail, Mr Kenny said he had seen numerous attempts to change the political system - many of which had failed.
He said no Government had made attempts to overhaul the Seanad in 70 years and that it was now up to the people.
The Taoiseach also defended estimates that scrapping the chamber would save the State 20 million euro a year.
Critics have claimed the true figure would be nowhere near as high, but Mr Kenny insisted it had been "independently verified" by the Oireachtas Commission.
"Clearly when the Seanad is abolished there will be no new senators elected, therefore there will be no new salaries to be paid," he added.
"Yes of course pensions will be paid until people move on as it were, and all of those who served the Senate and all of the facilities are no longer required, and the personnel who used them will be redeployed into other areas.
"These costings are independently verified."
The public will vote on Friday on whether to abolish the chamber, which is home to 60 senators.
Those campaigning to keep it, led by the opposition party Fianna Fail, have insisted it is necessary to serve as a government watchdog and to hold the ruling Cabinet ministers to account.
A new raft of political reforms introduced ahead of the referendum include longer sitting hours of the Dail to afford TDs more time to consider legislation.
Under plans to involve the public, committees will be able to consult advocacy, civil society groups and expert individuals at the pre-legislative stage.
Meanwhile, a second referendum will also be held on Friday on whether the State should set up a Court of Appeal.