"For far too long, too many people have come to the belief that there are no consequences when you come to San Francisco to commit a crime," Gascon said at a news conference this afternoon at the department's Northern Station.
Police are two weeks into a new enforcement operation by the department's vice squad and units from the Northern, Central and Tenderloin stations.
They're focused on a stretch of Polk Street and the surrounding area that they say has been the increasing subject of complaints by residents and merchants who see prostitutes operating openly on street corners, as well as drug use and other associated crime.
Police, politicians and prosecutors today touted their collective effort, with the announcement of 51 arrests in the past two weeks, most of them prostitutes and johns from outside San Francisco, police said.
"This is a joint effort," said Gascon. "This is community-based policing at its best."
Board of Supervisors President David Chiu, whose district includes the targeted area, acknowledged there had been "many frustrations" in the community leading up to the new operation.
"For the first time, everyone is really rowing together in the same direction," Chiu said.
Both Gascon and District Attorney Kamala Harris said that prostitution "is not a victimless crime."
While the reasons some take up prostitution are varied, Gascon said, "Very few have anything to do with glamour or choice."
The city offers education and treatment programs for those arrested for prostitution.
For those "beyond help," Gascon said police and city leaders need to develop the right tools to make it difficult for them to operate in San Francisco.
Prostitutes and johns come to San Francisco because they "could not get away with this behavior in their communities," said Gascon. He said prostitution brings with it drug dealing, fights, and needles and condoms strewn in front of people's homes.
"People should not be subjected to this type of behavior," Gascon said, calling it a "free-for-all in San Francisco."
The seven-days-a-week enforcement operation is tackling the area of middle and upper Polk Street, and a four-by-six-block area between Van Ness Avenue and Leavenworth Street, and between Sutter and Washington streets.
Police are using surveillance and undercover decoys in the operation. Most of the prostitution activity occurs there between 1 a.m. and 6 a.m., they said.
Police called it a "renewed" effort, similar to a stepped up prostitution enforcement about two years ago, sparked by a gun battle between two pimps fighting over territory at the nearby intersection of Pine and Larkin streets.
In that episode, one person was hit by gunfire and bullets flew through apartment windows and into parked cars, according to police Capt. Ann Mannix.
Of the 51 arrestees so far in the current operation, 36 were women soliciting for prostitution and 15 were male johns, police said. The women, many of whom had been arrested before for prostitution, hailed from Berkeley, Oakland, Vallejo, Fairfield, Sacramento and as far away as Los Angeles, San Diego and Las Vegas. Another was a juvenile girl from Santa Rosa.
Most of the men were also out-of-towners, from Mountain View, South San Francisco, San Bruno, San Jose and Santa Rosa, police said. Harris called the operation "a clear message."
"You come to San Francisco and you think you are picking up a prostitute, and that prostitute may very well be a police officer, so be careful," she said.
Gascon also floated the possibility of seeking new regulations allowing the towing of johns' vehicles and the publication of repeat offenders' pictures on the department's Web site.
"We're trying to come up with sustainable solutions to the problem," he said.
Ideally, Gascon said, police would not be making arrests in the same neighborhood every night, and further, the department does not have the staff to put officers on every corner or continue enforcement operations indefinitely, he said.
Gascon defended his controversial proposal to embarrass johns into taking their business elsewhere.
"Johns, typically, are not repeat offenders, he said. "We want to leave these more embarrassing moments ... for people who do not get it."