Updated

New York City Mayor Michael Bloomberg said Friday it's not always easy to spot a prostitute.

The subject came up during Bloomberg's weekly radio show when WOR host John Gambling asked him about an anti-sex-trafficking bill passed by the City Council on Wednesday.

The bill is intended to stop cabbies from knowingly driving prostitutes to meet their johns. One provision of the bill would enlist drivers to help steer prostitutes away from illegal activities.

But several young women rallied outside City Hall on Thursday to say that not everyone who looks like a hooker actually is one.

The women said they fear that if the bill becomes law, cabbies will be afraid to pick up women wearing short skirts or spike heels. "They don't even know who is a prostitute or not!" said Diana Estrada, who wears shorts or miniskirts to her bartender job.

An apparently sympathetic Bloomberg told Gambling, "If I were a young lady and I dressed in a sporty way ... and there's nothing wrong with that — maybe it's not appropriate to go to the workplace, but at night sometimes sure, why not — I would not want somebody thinking that I'm a prostitute."

The mayor said he did not know if the sex-trafficking legislation was a good idea or not.