Drug treatment programmes are only successful for around half of the drug addicts who enrol on them, figures have shown.
Health minister, Dawn Primarolo, said just 35,441 patients out of 69,612 were given "successful discharges" from structured treatment programmes in 2007-08. This works out at about 51%.
That left 34,171 patients who failed to complete their treatment for drug misuse, figures released in a written parliamentary answer to shadow home secretary Dominic Grieve showed.
This included 19,591 - or 28% - who simply dropped out or left, with a 2,169 turning down the treatment and 2,078 having treatment withdrawn. A total of 4,240 (6%) failed to complete their course due to be admitted to prison.
Of the successful cases, only 11% were considered to be "completely free of using illegal drugs". This totalled about 7,324 ex-users. The remainder were either using drugs in a "non-dependent way" or were referred on to other services.