The Tánaiste said it is not possible to exempt first time buyers from the concrete block levy.
Leo Varadkar said the levy is on the construction industry and he cannot see how any particular group could be exempted.
Taoiseach Micheál Martin suggested last weekend that the Government would be open to amending its controversial measure to ensure it does not penalise home buyers by forcing up new build house prices.
The aim of the 10% levy announced in the budget is to make the construction industry foot some of the multi-billion euro bill to fix defective homes.
It is set to raise €80m annually and due to be applied from April 3.
Mr Varadkar said: “I just don’t know how you would do that. The levy falls on a concrete block and I don’t see how you would be able to exempt any particular group.
“If you did do that, other groups would make a very good case for being exempt too.
“Take, for example, a family living in a very overcrowded apartment who are finally able to upgrade and buy a house for the first time. Would they then have to bear a higher cost? That’s always a difficulty when you try to exempt one group – you then put a bigger burden on another group.”
Opposition parties and housing organisations said the measure will result in higher house prices.
It could add up to €4,000 to the cost of an average three-bed semi-detached home, the Society of Chartered Surveyors Ireland estimated.
Sinn Féin called for the measure to be scrapped, saying it will put the “burden and pain” on homeowners rather on those responsible for construction defects.
Mr Varadkar, speaking after an industrial relations conference at University College Dublin, said the Government should “stand by” the levy because it has committed to helping homeowners.
“We’ve committed to spend a lot of money over the next decade repairing homes in Donegal and Mayo that need to be repaired,” he said.
“I think we’re going to have to make a similar commitment in relation to the defective apartment blocks in our cities.
“That’s a financial commitment of several billion euro even spread out over a number of years.
“I don’t think you can just say it comes out of general taxation. We need a revenue stream against that and the fairest way to do it is a levy against the construction industry.
“That’s what we intend to do.”
The Tánaiste reiterated that the details of the levy will be provided by the Finance Minister Paschal Donohoe in the Finance Bill.