Councilman Ben Kallos, a Democrat from the Upper East Side, sent a letter to the Buildings Department last Monday requesting an immediate stop-work order for the tower, arguing that the “unbuildable lot” could create a “dangerous precedent for a new and dangerous loophole.”

In March 2014, the department said the project could go forward with the adjacent lot along 88th Street. But at the time of that approval, the lot proposed by the developer was more than 30 feet deep — a size that could be developed into a separate building.

After that determination, the developers shrunk its size and filed papers with the city that created the new four-foot-wide property, known as Tax Lot 138. Plans describe the space between the building, Tax Lot 37, and the side street, designed as a garden for residents that is open to the street, as a “rear yard.”