Bowing to the construction unions, the United Federation of Teachers is pushing to derail a prized low-cost housing effort for educators because its developer shuns organized labor.

The project, two apartment complexes in the Bronx that would give educators exclusive preferences on more than 200 affordable apartments, is a partnership of the city comptroller, William Thompson Jr.; the city Housing Development Corp., and the city’s teacher pension fund, the Teachers’ Retirement System.

In October, the president of the teachers union, Randi Weingarten, applauded the plan as an innovative way to help teachers live where they work. Yesterday Ms. Weingarten retracted, asking the Teachers’ Retirement System to pull its $28 million in support for the project, more than half the cost.

She said she approached the fund after construction unions informed her that the apartment complex’s developer, the Atlantic Development Group, is not using union workers.

“This is what the labor unions should be doing for each other: We should be standing up for each other,” Ms. Weingarten said yesterday.

She said the project’s following prevailing union wage schedules had been a major condition of her support, and that city housing officials and Mr. Thompson’s office had assured trustees of the pension fund that it would be met. Ms. Weingarten said that after contacting the developer to demand proof of the agreement, she became convinced she had been “materially misled.”

The UFT is planning to picket the construction site today.

A spokesman for Mr. Thompson, Jeffrey Simmons, suggested he supports adding union workers to the project. “It is the comptroller’s hope and desire that this project can move forward in a positive manner, creating much-needed housing for our educators and providing fair wages for those involved in its construction,” Mr. Simmons said in a statement.

Neither pension trustees nor city housing officials could be reached for comment last night.