One of the last substantial pools of development rights in Manhattan — the equivalent in size to 11 Empire State Buildings — may find its way onto the open market over the next several years, compliments of the New York City Housing Authority.

The Housing Authority, which manages nearly 200,000 subsidized apartments in New York City, has plans to plug its $195 million budget gap by selling off development rights that are available at dozens of its affordable housing sites all over Manhattan, according to a report released by the office of the Manhattan borough president, Scott Stringer.

Those unused development rights — equivalent to about 30.5 million square feet — may represent one of the last frontiers for development in Manhattan, where private developers seemingly covet every square foot of valuable real estate.

These rights could be worth “billions” of dollars, according to Mr. Stringer, who is concerned the vast amount of space will be developed in a fashion that neglects public input. He is seeking increased oversight by elected officials in the approaching sale of the development rights.

“I am not here today to say don’t develop,” Mr. Stringer said at a press conference held yesterday on Manhattan’s Upper West Side, where he announced the findings of his report. “We are here today to say look before you leap. There has to be a larger discussion.”

The Housing Authority manages 178,350 apartments in 343 developments throughout the city, which service 406,000 low-income and moderate-income residents, and the Housing Authority controls the unused development rights at those sites as well.

According to the report, 85% of the Housing Agency’s unused development rights are spread across four districts: East Harlem, the Lower East Side, Central Harlem, and the Upper West Side.

A total of 24 developments have at least 500,000 square feet of unused development rights, and seven have more than 1 million square feet of unused development rights.

It is unclear exactly how the sale of those unused development rights could ultimately translate into new developments.

Some would likely be “infill” developments, in which additional residential or retail property is developed in and around the housing sites. There is also the possibility of transferring the available air rights to nearby lots.

The three-member governing board of the housing authority is appointed by the mayor, but the agency is considered a state agency and thus is not subject to the city’s land use review process — a process that gives community boards, the borough presidents, the city’s planning commission, and the City Council the last say on whether a development project can move forward.

In his report Mr. Stringer is not calling for a halt to the sale of these rights, rather that the sales be subject to an approval process equal to the city’s uniform land use review process.

The president of the Real Estate Board of New York, Steven Spinola, said he had commissioned a report a year ago looking into the prospect of building with unused development rights from public housing projects.

“I think that there are opportunities there,” he said. “But I am not going to suggest that every one could be developed tomorrow.”

Mr. Spinola said he could understand “the need for a process” in those instances in which the Housing Authority is selling air rights it owns, which are then transferred to an adjacent lot.

But, Mr. Spinola said, “I don’t know if Ulurp is the right process for a state agency.”

A spokeswoman for the Housing Authority, Millie Molina, issued the following statement: “We welcome the Borough President’s analysis and recognition of NYCHA’s efforts to develop a pipeline of 3,000 units under Mayor Bloomberg’s historic plan to expand affordable housing in New York City. We will review the recommendations in the report and look forward to a continuing dialogue on these important issues.”