The city’s comptroller, William Thompson Jr., a Democrat who is a possible 2009 mayoral candidate, wants to cut property taxes by $600 a year for a select group of senior citizens.

Mr. Thompson yesterday announced a proposal that piggybacks on Mayor Bloomberg’s $400 annual property tax rebate to all homeowners. Mr. Thompson is calling for an added $600 rebate to homeowners 65 and older who have annual household incomes of $66,050 or less and who are enrolled in a separate property tax reduction program.

The comptroller’s idea was criticized by several economists as poor policy and does not seem to have the backing from City Hall it would need to become reality. The comptroller has no power to set taxes in the city. But the initiative does offer an early signal of the kind of policies Mr. Thompson might pursue as a mayoral candidate.

Special tax programs of this kind require approval from Albany and are often dead on arrival without backing from the mayor. Yesterday, a spokesman for Mr. Bloomberg cast doubt on whether he would be on board.

“We will review the comptroller’s proposal, but significant budget deficits in the future make it difficult for the city to afford any tax decreases,” the spokesman, Jordan Barowitz, said.

In his preliminary budget proposal earlier this month, Mr. Bloomberg called on Albany to renew the $400 rebate, which is designed as a giveback to homeowners who had an 18.5% property tax rate increase that became law in December 2002.

The mayor used the rest of the budget proposal to address long-term imbalances in the budget, not to increase spending or decrease taxes.

Mr. Thompson’s proposal would cost the city about $50 million and would give about 81,000 eligible seniors a combined $1,000 in city property tax givebacks – $400 plus an additional $600.

While senior citizens’ advocates are behind it, several economists said targeted tax cuts are poor public policy and that if anyone needs property tax relief, it’s commercial and business property owners.

The director of the Empire Center for New York State Policy, E.J. McMahon, said that if unexpected surplus money is used for tax cuts, it should go to across-the-board cuts and be dedicated to “cutting tax rates, not cutting checks.”

“Targeted tax cuts produce no economic benefit and are simply a political ploy meant to stuff money in the pockets of favored groups of voters,” said Mr. McMahon, a tax and budgetary expert who is also a senior fellow at the Manhattan Institute.

The executive vice president and director of research for the Citizens Budget Commission, Charles Brecher, said the seniors being targeted did not seem to be a particularly vulnerable group.

“The income threshold is relatively high and it’s going to spread money around to people who, as a group, are probably least in need among all those paying property taxes,” Mr. Brecher said.

Mr. Thompson billed his proposal as a badly needed break for low- and-middle income seniors. In a letter sent yesterday to Mr. Bloomberg; the speaker of the City Council, Christine Quinn, and the head of the council’s finance committee, David Weprin, Mr. Thompson said seniors are being financially squeezed and a larger rebate would provide a needed relief.

“The rapidly escalating cost of home ownership, including higher assessed values, higher property tax rates, and increasing energy and insurance expenses has placed significant burdens on New York City seniors living on fixed incomes,” Mr. Thompson wrote.

“Some seniors may even face the risk of losing their homes,” the comptroller added.

Mr. Weprin told The New York Sun that it was a “terrific” idea and said he planned to introduce a resolution in the council to call on Albany lawmakers to support it. He said $50 million was a modest amount in a city budget of about $55 billion. “Seniors who are on fixed incomes that are in some cases house-rich, but barely have the money to buy prescription drugs or food, could use this relief.”

The director of public policy at the Council of Senior Centers and Services, Bobbie Sackman, said the threshold seemed “generous,” and said anything that allowed seniors to stay in their homes when they aged was a good idea.

A deputy comptroller, Marcia Van Wagner, said Mr. Thompson’s proposal was not designed to overhaul the tax system, but simply to provide temporary relief at a time when the city has the ability to do so. Mr. McMahon said the overall economy suffers through these types of proposals. “The tax structure in New York State is already a disgrace, this rebate simply makes it worse,” he said.