Cook County Sheriff Tom Dart filed a federal lawsuit Thursday against electronic message board giant Craigslist in an effort to get it to remove the portion of its Web site that he says is used almost exclusively to promote prostitution.

Craigslist was quick to respond that it routinely cooperates with law enforcement agencies and issued a statement saying "we work diligently to prevent" misuse.

"Misuse of the site is exceptionally rare compared to how much the site is used for legal purposes," the statement said, adding, "Regardless, any misuse of the site is not tolerated on Craigslist."

It went on to list 18 steps the site takes to try to prevent abuse, including telephone verification as a requirement for posting "erotic services," blocking ads with potentially inappropriate language, and a variety of notices aimed at warning against or preventing human trafficking. Guidelines posted at the site warn posters not to state or imply trading sex for money or post nude pictures.

However, a quick tour of the site plainly showed those instructions weren't working, with women posting fully nude pictures and hourly rates in their ads. "DROP DEAD GORGEOUS BLONDE $100 All inclusive - 19 (Schaumburg)" boasted one ad.

Dart contends the site hides behind the First Amendment, knowing it is being used for prostitution but winking and contending the site is for something else.

"There's no mystery. We all know what's going on here," said Dart.

Dart called Craigslist the "largest source of prostitution in America" based on surveys of sex-trade customers who indicated Craigslist as the main way they found prostitutes.

And while some may contend the site just facilitates a business transaction between consenting adults, Dart says it just promotes the misery and exploitation of women who are often abused by violent pimps.

"Like this is 'Pretty Woman,'" scoffed Dart. "This is not pretty stuff."

Dart says his officers often find juveniles when they respond to ads and show up to bust prostitutes.

Samir Goswami of the Chicago Alliance against Sexual Exploitation said a recent study of 200 prostitutes by a DePaul professor found that about half of all prostitutes have a pimp, and of those, about three-fourths said they would face harm if they didn't give their pimp a cut of the money earned.

"This meets our federal and state definition of human trafficking," said Goswami.

Ads in the "erotic services" section on Craigslist used to be free, Dart said. In recent years, under an agreement with 39 attorneys general, Craigslist has agreed to charge $5 for "erotic services" ads and donate the money to groups that aid those caught up in human trafficking.

Dart says he believes the service continues to allow the "erotic services" ads because they are the biggest traffic-generator for their site, allowing Craigslist to charge handsome rates for other legitimate ads.

Dart said criminal laws require a "closer nexus" between the advertising forum and the pimp in order to charge Craigslist with a crime. So instead, he is pursuing a civil suit that alleges the service is a public nuisance and is aware its activities are causing destructive consequences. Dart said he has been trying to negotiate with the site for two years, to no avail.

The suit seeks an injunction ordering Craigslist to remove the "erotic services" portion of its site and compensation for all the resources the sheriff has spent dealing with the site.

Site: Suit seeks removal of 'erotic services' ads