The Democratic speaker of the Assembly, Sheldon Silver, yesterday said he couldn’t support a plan to give parents private school tuition tax credits because there’s no guarantee from schools that they wouldn’t respond with a tuition hike.

A day before the Legislature’s deadline to reach a budget agreement to submit to the governor, Mr. Silver, who represents Lower Manhattan, spoke in detail about his opposition to Governor Pataki’s $500 tuition tax credit proposal and suggested that lawmakers would not approve a credit plan that is linked to educational expenses.

“The crux of the argument is as follows: Are those schools going to increase tuitions and take money from the parents?” Mr. Silver said. “That’s the real issue. The issue is under the governor’s program is every parochial school, every private school going to raise tuition $500?”

On the issue of education tax credits, Mr. Silver is in a tricky spot. The teachers unions, a powerful interest group in Albany, have declared such credits to be unacceptable. But the credits are backed firmly by the Orthodox Jewish constituency in Mr. Silver’s district and by the Catholic Church.

The speaker, who has asked religious leaders for an assurance that parochial schools wouldn’t use a tuition tax credit as an excuse to increase tuition, said he does not have a guarantee.

He criticized the governor’s plan for being restricted to school districts that have at least one school that is determined to be failing by federal standards. That approach, Mr. Silver, said would exclude low-income families who live in other areas.

He also said the Assembly’s statewide plan, which gives parents a tax credit per child of up to $300 and does not restrict how the money is spent, is superior to that of the governor’s because the Assembly isn’t telling people “how to spend their money.”

The Assembly’s credit plan encourages “people to have families” and recognizes the costs of raising children. He said, however, that he would not characterize the Assembly’s proposal as “pro-life.”

Tax credits are among several sticking points in budget negotiations. Both houses yesterday disagreed on details of a plan to create a Medicaid fraud inspector general, on how much property tax relief should be given to people outside of New York City, and on whether the state should reinstate a clothing sales tax for purchases of less than $110.

Lawmakers are likely to agree on a budget by today in time to accommodate a three-day “aging period” before the March 31 deadline. The governor has 10 days after that point to negotiate with the Legislature.