The mayor’s plan to make all welfare recipients work for their check might be the cornerstone of a national political run, but workfare will soon cost city taxpayers an extra $600 million a year, according to the city’s Independent Budget Office (IBO).

If the city Human Resources Administration continues with plans to require workfare participation of all but the most severely disabled recipients, costs will rise by a half billion dollars in 2000 and $601 million by 2002.

Even though the city is expected to shed an additional 100,000 welfare slots over the next several years, the cost savings will be fleeting. “Everybody on welfare, even the people who have workfare jobs, still gets their check,” said IBO analyst Paul Lopatto, one of the report’s authors. “The ones who have the workfare assignments also need to receive training, placement services and child care services. It adds up to additional cost.” Workfare’s price tag could top $850 million by 2002 if the city falls into an early-’90s-type recession and caseloads climb, IBO estimates.

The cash crunch will be especially tough in 2002, when some 50,000 recipients are expected to lose their benefits under the federal five-year time limit. The state and city have agreed to create a Safety Net Assistance program that will tack an additional $124 million onto the city’s budget to help ease the welfare refugees into the workplace.

Since 1995, Giuliani has slashed the welfare rolls by 253,000, largely by forcing people who won’t or can’t take workfare jobs off the dole.

IBO, an autonomous city agency that has frequently tweaked the administration, harshly criticized the mayor for failing to track former welfare recipients to see if workfare prepared them for employment. A recent survey by the State Office of Temporary and Disability Assistance found that a 22 percent of ex-welfare recipients who dropped off the rolls in March 1997 made at least $100 during the first three months on their own.

Last week, city welfare boss Jason Turner released the results of a phone poll of 126 former public assistance recipients showing that only a third had failed to find some kind of job. But the survey’s minuscule sample size and phone-it-in methodology elicited jeers from welfare advocates.