Experts in the UK say sending convicted drug users to prison does more harm than good.
A new report from the Drug Policy Commission, an independent panel, says as many as 65,000 prisoners in England and Wales are thought to be problem drug users and two-thirds of these are convicted for the less serious crimes of shoplifting and burglary.
The commission believes these offenders should not be jailed and suggests community treatment programmes would be more effective than prison.
Almost a third of heroin and crack users arrested admit to committing an average of one crime a day, but the Commission is concerned that drug treatment programmes in prisons have failed.
The commission's report is highly critical of the quality of treatment in jails, where "provision often falls short of even minimum standards and is a major concern for the health and well-being of prisoners and the subsequent impact on crime".
The commission says not only have they not worked but inmates are at risk of infection from blood-borne viruses.
In excess of £330m is spent in England and Wales on treating offenders annually and the commission says some treatment services such as the Carat service, risked doing more harm than good; the Carat service took on 78,000 new prisoners last year.
The commission has found for the 40,000 prisoners who go through 'detox' while in jail, a lack of proper aftercare meant many went straight back to using hard drugs when they left prison and 1 in 200 injecting heroin users would be dead from an overdose within a fortnight of being released.
The problem of drug use in prison is an increasing one and research has revealed that heroin use is now more widespread than cannabis.