A cop who accused her NYPD boss of trying to push her into a threesome with his wife has filed a lawsuit against the department.

Officer Maribel Sarante said Sgt. Freddy Lopez, her supervisor at the Seventh Precinct on the Lower East Side, retaliated against her after she turned him down and reported him, according to Brooklyn federal court papers filed Monday.

The NYPD sweeps gender-bias cases under the rug while promoting “unqualified employees such as defendant Freddy Lopez who then further ‘prey’ upon other female employees,” according to the suit, which names the city, Police Commissioner James O’Neill and Lopez among its defendants.

Sarante, who still works for the department, alleges Lopez asked her for the ménage à trois in 2015 by saying “his wife gives him no ass” — then tried to frame her for fudging time sheets when she turned him down.

Her lawyer, Eric Sanders, said Sarante’s complaints the department were ignored.

“Each time she made a complaint they said it didn’t rise to a certain level,” Sanders told The Post. “They just don’t take sexual harassment, or any forms of discrimination, seriously.”

Sarante claims the sergeant knew she was married with kids when he made his proposal.

She also charges in her suit that only 10 percent of gender-bias cases targeting city cops are ever substantiated because the system is stacked against their accusers.

The NYPD and the city’s Law Department did not comment. Lopez did not return calls for comment.