The Government has been accused of ignoring a "fundamental canon of taxation law" in its property tax proposals.
Fianna Fáil leader Micheál Martin said "ability to pay" was an essential element for the implementation of property tax but half a million people were living in houses in mortgage arrears.
"Yet for some unknown reason, they're being expected to pay a significant family home tax, all in the context of a dead property market," Mr Martin said.
He added that there are "many, many people" who don’t have it to pay the tax. "We're talking about the unemployed people on welfare payments, pensioners, people on family income supplement, the lowest income of those working."
He said it was "essentially a very unfair tax because absent from the tax and its legislation is a fundamental canon of any taxation law which is ability to pay".
He said people "don’t have the capacity to pay the level of property tax that’s being put on them".
Mr Martin insisted: "It's the wrong time to put the tax on people."
But Taoiseach Enda Kenny said Mr Martin in government had signed on for the property tax. Mr Kenny told him: "Now, like St Augustine, you want to be made pure but not just yet."
The Taoiseach said the position was as outlined by the Minister for Finance in the Budget. The house valuations would be set based on bands of €50,000. The tax would be at 0.18 per cent of the value of the property and at 0.2 per cent for houses valued at more than €1 million.
"The Minister has outlined the understanding of the difficulty people have these days in the economic circumstances the country finds itself," he said. Allowances were being made for people in difficulty, he said.
Explaining the basis for the tax, Mr Kenny said it aimed to broaden the tax base. He pointed out that local authorities had found an "easy way to increase rates" on commercial premises. He said most of the tax would be used for services in the area where it was paid.
"That's why the banding is fair and more progressive. The deferral options are there for those who find themselves in particular difficulties."
