As the state Legislature works on revising a tax break for New York City developers, the law could see new, more expansive provisions for affordable housing. Any added requirements, however, undoubtedly will raise hackles within the real estate community.

With multiple bills expected to be introduced in the next few weeks, a number of state legislators are pushing to expand the scope of the existing law — a residential development incentive known as Section 421-a that originally passed in 1971 — by adding significant new affordable housing requirements for developers seeking to qualify for the tax break.

The current law, passed at a time when new construction was scarce, allows developers to get a tax break on projects built in most parts of the city, and has been an attractive incentive that has spurred construction. While housing advocates say the proposed changes in many of the bills would provide incentives to build muchneeded affordable housing, the real estate industry has long been opposed to any alteration in the subsidy, claiming the proposed regulations would slow a residential construction boom of historic proportions.

Similar negotiations over Section 421-a abatements occurred in the City Council last fall. In December, after weeks of debate, the council passed changes that expanded the law’s affordability provisions. Under the council’s provision, in order to get the tax break, developers will be required to make 20% of a new building’s units available at rents affordable to people making 80% of the area’s median income. The revised abatement, whose benefits vary depending on location, level of government assistance, and other factors, will be available in a large portion of Manhattan, and in designated areas in Brooklyn and Queens. For the changes to take effect, however, the state needs to pass its own version of the law, which is set to expire at the end of this year.

Analysts say any bill likely to pass in Albany will probably expand affordable housing requirements at least moderately beyond what the City Council proposed, a move that would further irritate developers already angry over the council bill’s passage. Bills currently in the hoppers of the state Senate and Assembly mandate that developers make 30% of their housing units affordable at sites citywide, 10% more than what the council’s law proposed, in order to qualify for the tax benefit.

The real estate industry has been speaking out against aspects of the proposed changes for months. The president of the Real Estate Board of New York, Steven Spinola, said yesterday that the City Council’s law was too restrictive.

“I’m not going to hesitate on that: I think the mayor’s proposal and the City Council went way too far,” Mr. Spinola said. “I believe this is going to have a negative impact on the building of affordable housing, and the building of housing.”

State Senator Elizabeth Krueger, a Democrat of Manhattan, who is planning to introduce legislation that includes affordability provisions even more expansive than those of the current bills, said existing incentives have more room for restrictions.

“Everyone is building everywhere,” Ms. Kruger said. “Nothing we do with 421-a is going to stop building in New York City.”

The politics of the issue are such that the influence determining the final form of the changes will likely lie with the state Senate’s four New York City Republicans, legislators say. A proposal in the Democratic-controlled Assembly seems to have strong early support; in the Republican-controlled Senate, the majority leader, Joseph Bruno, may defer to the local legislators because the law only applies to the city.

Senator Serphin Maltese, a Republican of Queens, is sponsoring a bill that expands the affordability requirements of the law, though other area Republicans have not yet signed on, and is optimistic about its chances.

“Senator Bruno has been always very responsive to me and the New York City Republicans,” Mr. Maltese said in a phone interview. “There’s no city in the United States that needs affordable housing more than New York.”

A spokesman for Senator Frank Padavan, a Republican who represents parts of Queens, the Bronx and Nassau County, said he supports a bill similar to that passed by the City Council, but that he did not support Mr. Maltese’s recent bill. (Republican Senators Martin Golden of Brooklyn, and Andrew Lanza of Staten Island, did not return calls for comment by press time.)

The city’s other major Republican office holder, Mayor Bloomberg, does not have any direct power in the legislature, but is likely to push for a bill that mirrors the law passed by the City Council and signed by the mayor.

“We hope that the legislature sees the large consensus from the City Council and the mayor in the legislation that was passed in December, and considers that as it looks to extend 421-a,” a spokesman for the city’s department of Housing Preservation and Development, Neill Coleman, said.