An unpublished report has revealed that Lambeth is home to a quarter of all London's youth gangs.
Police estimate there are at least 171 gangs across London
Research commissioned by Lambeth Council found there were 40 gangs operating in the area, with one gang thought to have 2,500 members.
Researchers linked the growing number of gangs with rising violent crime among young people.
Lambeth Council will be holding a 'gang summit' on Thursday to thrash out an action plan on the problem.
The report, to be published on Thursday, found young people joined gangs for a variety of reasons including "fun and companionship, fear and coercion."
Gangs were located in the borough's poorest areas such as Acre Lane, Stockwell Gardens Estate and the Tulse Hill Estates.
Most gang members were African-Caribbean with a few who were white or Asian.
Researchers said most gangs were composed of "elders" in their late teens and early twenties, and "youngers", aged around 14 to16, sometimes aided and abetted by "girlfriends".
"Elders" made their money from drug sales while "youngers" benefited from street crime.
By late last year, gang conflict was becoming more violent leading to no-go areas for outsiders, researchers warned.
However, the Peel Dem Crew, which was highlighted in the report, hit back at the findings.
Ja Ja, the gang's leader, said members were now involved in the music industry: "A couple of years ago, we were on 'active street duties', but that's outdated now."
"We've been to prison, come out, we're grown up now. We're official businessmen now. We don't take part in any criminal activity."
Lambeth Council plans to outline several recommendations to combat the issue.
They include a new intelligence gathering unit to target young criminals, youth centres being open seven days a week and a hotline for worried parents.
Cllr Lorna Campbell said: "We already know that guns, gangs and knife crime are the major issues for many young people and families in Lambeth."
"This report and this summit is about getting to the heart of those problems and finding real solutions."