Re-offending rates among young men are not being adequately addressed by the government, according to a report.
The study says more constructive work is needed
The Howard League for Penal Reform report studied 86 offenders aged 18 to 20 in England and Wales.
It said young men had high offending and re-offending rates but were largely ignored by initiatives to cut crime.
The Home Office said reducing re-offending was a priority, and that a strategy and standards were being developed for managing young offenders.
Report author Finola Farrant said: "Sending these young men to prison does virtually nothing to ensure that they will live crime-free lives on release."
She added that prison could make their re-offending "all the more predictable".
More than 1,000 young men are sent to prison each month, and it costs £35,000 a year to keep them inside, said the Howard League.
But its study - called Out For Good - claimed little constructive work took place in prisons or on release, and that nearly 70% of those released from prison would be re-convicted within two years.
The report calls for changes in the way services approach working with young men to reduce their offending.
When asked what would help them stop committing crime, 55% of the 86 young men who took part said getting a job, and about a quarter said stable housing would help.
Ms Farrant told BBC Radio 4's Today that being in a relationship and "having far more constructive relationships with their families" were also identified as positive influences.
Out for Good concludes that the current system does little to ensure young adult offenders make amends for what they have done, or recognise the impact of their behaviour on individual victims, their families and the wider community.
Ms Farrant said: "Such criminal neglect of young offenders puts the public at risk of further offending."
Chief Inspector of Prisons Anne Owers said that in 2000 resources for under-18s in prison, such as education, training and support during and after imprisonment, had been improved, but that the same had not been done for young adults.
"It is very clear we need to put more resources in to make sure that we are not just creating, as the Howard League is saying, a revolving door for these young people," she said.
"Wherever they are, whether they are in prison or outside in the community, we need to put resources into turning lives around at a time when they can be turned around so that what doesn't happen is that they get launched on a career of offending, which is sadly happening to all too many of them."
Responding to the report, the Home Office said: "The National Offender Management Service is developing a strategy and standards for the management of young adult offenders, both in custody and the community.
"This covers key areas like jobs, housing, health, drugs and alcohol, and offenders' families."