Only one in 10 people believe that jail helps young offenders become law-abiding citizens, according to a survey.
A poll of 1,000 adults by ICM for SmartJustice, which campaigns for alternatives to prison, also found two out of three regard jails as "universities of crime".
Instead, about eight in 10 people surveyed supported better mental health or addiction support.
Nine out of 10 backed better support by parents and more activities for young people.
SmartJustice director Lucie Russell said: "People no longer believe that locking up young criminals and throwing away the key achieves anything.
"The Government needs to sit up and listen to what the public are saying.
"Prison is an expensive way of making non-violent young offenders worse."
Eight out of 10 interviewees (84%) backed compulsory work in the community combined with drug treatment for young drug addicts.
