A scheme which created “shooting galleries” for heroin addicts has led to big reductions in the use of street drugs and crime.
The pilot, part of which was carried out in Brighton, saw users administered the drug or a substitute in supervised NHS conditions.
The results, which were published today, showed those who were injected with heroin made “marked improvements” in their general health.
Leaders behind the project are now asking Government ministers to set up further trials to tackle misuse in the city, which was recently declared the drugs death capital of Britain.
Morag Murray, of the Sussex Partnership, who helped run the project, said: “These findings show that it is possible to effectively treat those people with a severe and enduring crime-funded heroin addiction, who previously found it difficult to engage with services.
“Participants who received clinical injectable heroin during the trial were long-term drug users, previously spending about £300 a week on street heroin to fund their addiction.
“They are now spending on average less than £50 a week, with a significant proportion completely cutting out their use of street heroin altogether.
“There was also reduced use of other drugs, such as crack cocaine, and marked improvements in both physical and mental health and social functioning.
“We now need to wait for policy makers to decide how to best apply these findings.”
The Randomised Injecting Opioid Treatment Trial (RIOTT) programme involved more than 100 users nationally in centres in Brighton as well as London and Darlington.
Many of the clients, who were all self-referred, had been identified as the hardest to treat.
During the trials, a third of addicts were given methadone, a heroin substitute, orally and another third had it injected under supervision.
The remainder, observed by nurses, injected themselves with diamorphine - unadulterated heroin - imported from Switzerland.
Psychological support and help with housing and social needs was also offered.
After six months, the heroin injecting group had committed two-thirds less crimes - a fall from 1,731 to 547.
Project leaders say the scheme, which costs £15,000 per user every year, is cost effective as it helped avoid “expensive” prison sentences.
Independent expert group The National Treatment Agency for Substance Misuse said there was enough "positive evidence of the benefits" to merit further pilots.