The number of New Yorkers losing their homes to foreclosure jumped by a third compared with a year ago, a study has found – and experts are warning that the worst is yet to come.

New York-area foreclosures are up 34 percent for the first quarter of this year, which is far lower than the national rate that roughly doubled over last year, according to a report released yesterday by RealtyTrac, an online real-estate service.

Analysts once predicted that New York’s real-estate market would be largely insulated from the wave of home-loan defaults affecting much of the country. But lawmakers and local organizations are now working overtime to keep up with the volume of requests for help from homeowners in crisis.

New York’s foreclosure process is unusually long, taking more than a year for defaulting homeowners to lose their homes, so experts say the data probably does not reflect the level of foreclosures that will hit the area.

“We are still waiting for the other shoe to drop,” said RealtyTrac spokesman Daren Blomquist about the foreclosure rate in the city.

Rep. Nydia Velazquez (D-Brooklyn/Manhattan) said she has heard from many of her constituents in Brooklyn who are desperate to keep their homes. But she said she is anticipating an even larger spike in foreclosures later this year as interest rates on adjustable-rate loans soar.

“They call because they don’t know what to do,” she said of homeowners who have contacted her office for help.

In Brooklyn, one in every 241 homeowners is now in the foreclosure process. That is more than double the number of Brooklyn households in that situation a year ago.

Even in Manhattan, with relatively strong property values, foreclosures have increased 66 percent since the first quarter of 2007, and Queens’ numbers are up 41 percent.

Staten Island may be the hardest hit among the boroughs, with 737 foreclosures representing a 101 percent increase in the first three months of this year over the first quarter of 2007.

New York’s suburbs have not been spared. In Westchester County, foreclosures are up 138 percent this year, the report found.

Overall, the metropolitan area rates 80th among the top 100 regions most affected by the foreclosure crisis.

Nationally, the foreclosure crisis is hitting the West hard.

Stockton, Calif., is first on the list of metropolitan areas with the most foreclosures per household, with one in every 30 homeowners receiving a foreclosure notice.

The state with the most foreclosures is Nevada, where one in 54 households is in foreclosure.

A Census Bureau report released yesterday found that the number of homes sitting vacant nationwide hit an all-time high of 18.6 million in March, which was attributed to the rise in foreclosures.

The bureau’s regional data, however, showed that the vacancy rate remained virtually unchanged in the Northeast.

daphne.retter@nypost.com