The city finance commissioner said she will be reviewing the city’s complicated property tax system over the next six months and that among the ideas under consideration is the possibility of changing the system that charges co-op and condominium owners more than regular homeowners.

“The property tax structure has to be fixed,” Martha Stark said after speaking yesterday morning on a panel about New York’s tax burden organized by the Citizens Budget Commission.

Ms. Stark said no proposals have been hammered out yet but that the property tax system needs to be more transparent and fair and that she hoped to “take the show on the road to Albany” once proposals are finalized at the city level.

A spokesman for the finance department, Sam Miller, later said the commissioner’s top priority is to deal with the disparity between New Yorkers’ incomes and their property tax bills going up. He said merging property tax classes is “one potential option of many.”

Ms. Stark also said she’d like to see increases in income eligibility requirements for senior citizens and those on fixed incomes to help more of them qualify for lower property tax rates. Last week, she issued a statement saying that “any reform effort must start by addressing the public’s legitimate concerns about the disconnect between growth in the market values and changes in income.”

The commissioner’s comments come a week after the city’s Independent Budget Office released a report showing that the four-tiered tax system in the five boroughs favors homeowners over renters and commercial buildings.

The issue of changing the system is a politically charged one because homeowners, particularly those concentrated in the politically potent boroughs outside Manhattan, are favored under the current system.

To highlight the wide disparities between different property class owners, the Citizens Budget Commission showed a slide yesterday using Mr. Bloomberg’s $10.5 million Upper East Side townhouse as a hypothetical example.

Under the current system, Mr. Bloomberg pays $72,633 a year in property tax, according to the slide. If the current assessment caps — which allow only a 6% assessment increase a year — were lifted, Mr. Bloomberg would pay $98,586, because his home would be valued at a higher amount.

But his tax bill would dramatically change if his townhouse were classified in a category other than class one, which includes one, two, and three-family residences. If the townhouse were a large rental building, for example, he would pay about $585,000 a year in tax, the chart estimated.

The city’s four-class tax structure went into effect 25 years ago after the state’s highest court ruled that New York’s system for taxing homes and buildings violated the state constitution because similar houses in different neighborhoods often had very different tax bills.

The research director for the Citizen Budget Commission, Charles Brecher, who was on yesterday’s panel, said the city needs to “equalize rates among residential properties in a fair way and begin to move some of the burden off business properties so that the economy can grow.”

“The way it works now has serious harmful economic consequences,” he said after the event. “We’re really putting the least burden on people who can probably afford it most, giving the biggest breaks to the homeowners.”

“I think it would be one of these tests of what a term-limited mayor who wants to do something for the long run of the city is willing to go after,” Mr. Brecher added. “Politically it has been something of a third rail.”

A spokesman for the mayor, Stuart Loeser, deferred to the finance department.

The chairman of the city’s Finance Committee, David Weprin, acknowledged that the current system is not fair to co-op and condo owners. He noted that co-ops and condominiums are currently assessed at about 40% of market value, while single-family homes are assessed at 8%.

“But if you all of a sudden brought the property taxes of single family homes up to 40% of market value you would have a lot of foreclosures, you would have people that couldn’t pay the property taxes,” said Mr. Weprin, who represents an area of Queens where homeownership is high.

He said he expected the city to “try to find some relief for co-op and condo owners,” but that homeowners need to be protected in that process.

During the panel discussion, which hit on a wide range of tax issues, Ms. Stark also raised the prospect of creating “one business tax structure for all firms.” She said was a preliminary idea that she has not yet discussed with the mayor..