The developers offered $54 million for air rights, in exchange for building a pair of tall towers next door, in what seemed like a deal too good to refuse. But on Thursday, the board of the Seward Park Cooperative on the Lower East Side said that the deal had failed to win approval from residents, in what some shareholders said was a symbolic message about overdevelopment.

“I’d like to think this would send a signal to the general community in favor of sensible, incremental development,” said Bill Ferns, a resident of the complex who opposed the deal. “We don’t want the character of who can live in this neighborhood to change radically.”

The vote only blocks the builders from erecting two towers taller than zoning laws permit; the developer, Ascend Group, has said it still intends to build, though at a lower height.

After 17 months of negotiations, the board of the Seward Park co-op had recommended approving the lucrative sale of 162,000 square feet of unused development rights as a way to ease the financial pressure on the four-building residential complex.