When Philadelphia Police Officer Annamae Law arrived at district headquarters, she says, the place was buzzing.

” ‘You should have been here,’ ” she said one officer told her. ” ‘You missed the show.’ ”

Here’s what she missed, according to sworn statements of two women: An officer in a Fishtown police station had forced them to put on a sex show in a jail cell, ordering them to expose their breasts and kiss as a price of release.

“It was so uncomfortable and degrading,” Erica Hejnar, one of the women, said in an interview. “I couldn’t believe it was happening. I kept saying, ‘Why are you doing this to us?’ ”

Today, three years after the women reported this bizarre episode, the case remains open. Even though an outraged Law says the “show” was the talk of the station house, no officers have been arrested or disciplined.

The allegations highlight a persistent but hidden problem in law enforcement: police officers who use their badges to exploit women or extort sex, and departments that fail to vigorously investigate such abuse.

“The women are terrified,” said Penny Harrington, the former police chief of Portland, Ore., and founder of the National Center for Women and Policing. “Who are they going to call? It’s the police who are abusing them.”

When women do come forward, their complaints are often ignored.

Indeed, experts say, culprits tend to target vulnerable women such as prostitutes, drug addicts or drunks, knowing they likely won’t be believed.

“You don’t pick the mother of three, the soccer mom. You don’t pick the prom queen,” a prosecutor said during a 1997 trial of a Norristown police officer convicted of sexual assault.

“You pick the delinquent kid. You pick one of the street crawlers, people out there at 4 in the morning.”

The extent of the problem remains concealed from the public - and police chiefs - because departments often lump sex-abuse allegations into such categories as “conduct unbecoming.”