YONKERS - City officials are bracing for another assault on Yonkers' tax base after the number of people challenging the assessed value of their homes last month more than doubled over the previous year.

Some 1,054 residential property owners challenged their property assessments, up from 475 last year, and more than 10 times the 98 that were filed three years ago, according to the Yonkers City Assessor's Office.

The increase reflects the nation's plummeting real estate market and, City Assessor Mark Russell said, is likely to be an ill omen for future tax revenues, which are based, in part, on property assessments.

What's more, the numbers are likely to serve as a warning to some other municipalities, such as White Plains, where property owners can challenge assessments in January. White Plains has seen a steady if less dramatic increase in assessment challenges, rising to 522 in January 2008, from 427 the previous year and 267 in 2006. The White Plains figures include commercial and residential challenges.

The increase in residential challenges has renewed calls for a Yonkers revaluation. The last citywide reassessment was done in 1954. Outdated assessments mean that the city's 36,000 properties are assessed at an average of 2.34 percent of market value, significantly increasing the chances that properties are not uniformly valued, Russell said.

City Councilwoman Joan Gronowski, D-3rd District, recently reintroduced legislation for a revaluation, a proposal put on hold earlier this year when Mayor Phil Amicone said he preferred that the city's revaluation come as part of a larger Westchester County effort.

"I don't know what the chances are for a countywide revaluation," Gronowski said last week. "Meanwhile, we have other municipalities also looking into this."

In all of Westchester, only Pelham and Rye town have undertaken a full revaluation in recent years. Yonkers is by no means the municipality with the oldest assessments, however; Mount Vernon holds that claim, with assessment rolls dating back to before the Civil War, according the New York state Office of Real Property Services.

While the number of residential property challenges in Yonkers has jumped dramatically, the number of commercial challenges has remained roughly the same - numbering in the 900s annually for the past five years. That's because commercial owners have been routinely challenging their assessments as a normal part of doing business, Russell said. Though the increase in residential challenges is significant, it is not without precedent. The real estate bust of the early 1990s saw about 1,800 residential challenges, Russell said.

This year Yonkers had to return $5.2 million to property owners who successfully challenged their assessments, an increase from settlements valued at $3.7 million the previous year, and no settlements in 2005.

Revaluation is often considered the third rail of local politics, striking fear into hearts of property owners who worry that revaluation will result in sharply higher property taxes. Supporters of revaluation say the number of people seeing an increase in taxes as a result of the revaluation is typically balanced by the number who see a decrease.

Lee Kyriacou, executive director for the state Office of Real Property Services, told the City Council at a recent meeting that revaluation was the only way to assure tax fairness, assuring that owners of similarly valued homes pay similar taxes.

City Council President Chuck Lesnick said he hoped to get at least four votes on the council in favor of revaluation. A fifth vote would ensure that the plan could survive a veto from Amicone. Amicone's office did not return several calls placed yesterday.

"I'm hopeful that the Yonkers City Council will want to do a revaluation, regardless of what the county decides to do," Lesnick said yesterday.

A revaluation would quickly pay for itself, Lesnick maintained, by eliminating the need to refund property taxes as a result of successful challenges to the city's assessment system.

The cost of revaluation varies from roughly $100 to $125 per parcel, Lesnick said, amounting to a cost of $3.6 million to $4.5 million, money that could be borrowed the same way the city borrows to pay the tax refunds. New York state provides $5 per parcel to help municipalities conduct less expensive annual updates.