State lawmakers’ refusal to extend eligibility rules for a controversial property tax break could imperil projects to build 2,600 apartments for working and middle-income tenants across the housing-starved city, The Post has learned.

A project list assembled from sources in the real estate industry contains 17 already-approved plans in four of the five boroughs to construct nearly 10,000 new units — including market rate apartments. About one-quarter of the units would be set aside for below-market rate rents.

Mayor Eric Adams warned it would be a setback for the city if the legislature fails to extend the 421-a tax abatement program for projects in the pipeline before the program lapsed last year.

Lawmakers are scheduled to finish work Thursday for the 2023 legislative session.

“This is not hypothetical — New Yorkers are going to lose out on affordable housing if Albany doesn’t act now; tens of thousands of apartments in projects that are approved and ready to go,” Adams said in a statement to The Post.

“New York City has done our part, now we need the state Legislature to pass a 421-a extension and other affordable housing bills.”

Losing the apartments could worsen the Big Apple’s housing shortage, which has reached critical condition in recent months.

Rents across the city have soared to record levels as already anemic levels of housing production have ground to a halt.

Just six new apartment buildings were permitted last month across all five boroughs  — and none were in Manhattan, Borough President Mark Levine tweeted over the weekend.

“This is a five-alarm fire,” Levine said. “We need action to address our housing affordability crisis….Extend the 421a deadline.”

He also supports legislation making it easier to convert office space to housing, and strengthening rent protections statewide.

Most of the affordable 2,600 apartments would be set aside for families of three making between $76,000 and $102,000 annually.

Eight of the 17 new developments — nearly half — are in Brooklyn’s Gowanus neighborhood including: A 654-unit complex on Nevins Street along the Gowanus Canal with 164 units below market; a 1,030 unit project at 459 Smith Street, with 258 units set aside for lower rents; and an 815-unit project at 175 Third Street, with 244 units set aside for affordable rents.

Two of the other major projects are in western Queens: 1,400 unit Hallets North in Astoria, with 350 units below market and the 600 unit Core Long Island City, with 180 affordable apartments with significantly lower than market rents.

The failed push to build more affordable housing this year has been a major disappointment, advocates say.

Gov. Kathy Hochul in January proposed a sweeping housing plan to build 800,000 units that would have required suburban communities to build more new homes and higher density apartment complexes near commuter rail stations.

Lawmakers opposed the heavy-handed approach, and sought to rely on an incentives-only program. No agreement could be reached as part of the state budget approved in April.

Meanwhile, landlords pushed back against measures to expand tenant protections and cap rent increases statewide, called the “good cause eviction” bill.

Senate and Assembly negotiators declined comment Sunday.

Assembly Speaker Carl Heastie (D-Bronx) said last week the property tax break sought by Adams and developers is tied to other legislation backed by tenant activists — and that it’s difficult to do one without the other.

“Part of the challenge is that there’s, I’d say things that developers want, I think there’s things that I’d say tenants want. I think it’s difficult, these things are all kind of connected,” Heastie said.

“I don’t know if it’s going to be easy to pull one off and then leave everything else. I don’t know if people I’d say are okay with doing that.”

Senate Majority Leader Andrea Stewart-Cousins (D-Yonkers) also said last week the fate of affordability housing measures were still up in air.

“I’d like to think that we can come up with something that would be good for housing in New York before we leave, but I have nothing to report,” she said.

When asked Sunday about the 421-a property tax abatement program, a Hochul spokesperson referred to the governor’s previous remarks.

“I know they’re looking at a lot of different ideas and they know that I want to achieve this together. And that’s the path we’re going to be on, is figuring out a path forward together. And so, we’re doing a lot of convening now, but also over the summer heading into the fall,” Hochul said.

“And what else can be accomplished by Executive Orders, what opportunities I have as Governor to find ways to create more housing on State-owned properties, for example, areas where I can achieve more.”