The American Civil Liberties Union is calling on the Newark Police Department to stop considering prostitution a crime after a series of sex-crime busts.

Newark police arrested four women and nine men Friday in a large prostitution investigation. Seven vehicles were also towed away in the bust.

The ACLU says that making prostitution a crime is a poor use of the police department's limited resources and also impairs public health.

"These arrests harm public health by stigmatizing sex workers and making their lives more difficult and dangerous," a spokesperson for the ACLU says in a statement. "These crackdowns harm public safety by stoking fear of police among sex workers, dissuading vulnerable communities from reaching out to police to report abuses."

Newark Police Director Anthony Ambrose tells News 12 New Jersey that the investigation arose due to the amount of complaints by neighbors in the area.

"My office gets inundated by calls saying that people are buying sex in front of their houses...they're having sex in cars. My officers are doing what they have to do," Ambrose says.

Ambrose says that it would be irresponsible for his officers to turn their backs on prostitution.