He testified before the city's Public Safety Committee, estimating that the city has 39,000 gang members.
Cardenas said 10 percent of them are responsible for 80 percent of all the crime in the city.
Cardenas suggested expanding current programs aimed at preventing kids from joining gangs and reducing gang violence.
The city's current gang programs are run by the mayor's office with a budget of $26 million.
The mayor's office criticized the proposal to create a new department.
