Poll: Sinn Fein plans to increase rates for houses worth more than £400k - do you approve?
SF's 'grossly unfair' rates shake-up could cost people £6,000 a year, says SDLP
The SDLP has vowed to fight "tooth and nail" against a Sinn Fein proposal to increase rate bills for up to 7,000 homes.
Belfast councillor Declan Boyle described the proposed rise as "grossly unfair".
He also said the cash for ash scandal showed the Executive could not be trusted not to squander ratepayers' money on "hare-brained projects".
Councillor Boyle and South Belfast MP Dr Alasdair McDonnell are organising a public meeting next month to oppose the removal of the cap on domestic rates.
Sinn Fein Finance Minister Mairtin O Muilleoir announced what he called "the biggest shake-up in rating policy in a generation" last month.
Under the current system, a house with a rateable value of more than £400,000 has its rates bill assessed as though it was valued at £400,000.
Rates are property taxes paid by households and businesses, and are based on the value of the property.
But Mr O Muilleoir wants rates to be levied on the portion above £400,000 in order to ensure a "more proportionate contribution" from those in high-value homes.
It has been estimated that this would raise around £4.5m for the Executive. But the DUP in November voiced support for the current rate.
Councillor Boyle said he had been inundated with calls from residents in his south Belfast constituency who fear their rates could double, leaving them with bills of up to £6,000 per year.
Above - Check out Northern Ireland's 10 most expensive homes December 2016
He also claimed there were many pensioners living on meagre incomes, but whose houses had a high rateable value.
"The idea that people in big houses can well afford a rise in rates at first may seem reasonable," Mr Boyle said.
"But it's based on the totally wrong perception that residents of Stranmillis, Lisburn and the Malone Road are all loaded.
"There are plenty of people who worked hard to buy their homes, but whose incomes have shrunk considerably through time or circumstance.
"If rates are to rise, it would be fairer to introduce means-testing, rather than to hand someone a huge bill based purely on their address."
Councillor Boyle said the property crash meant that the rateable value of many homes in south Belfast was substantially higher than their current market value.
"People are being asked to pay rates based on an old valuation that is totally unrealistic today," he added.
"And homeowners don't deserve another property tax. They already paid one when they bought their houses - stamp duty."
Mr Boyle also claimed ratepayers had no faith that the Executive would use their money wisely. "They fear that this will be another few million going down the Stormont drain," he said.