A scheme in which heroin is given to addicts in supervised clinics has led to big reductions in the use of street drugs and crime, the BBC has learned.
More than 100 users took part in the pilot - part funded by the government - in London, Brighton and Darlington.
They either injected heroin or received the drug's substitute methadone.
Those given heroin responded best and an independent panel which monitored the scheme over six months is advising ministers to set up further trials.
About three-quarters of those given heroin were said to have "substantially" reduced their use of street drugs.
Research suggests that between half and two-thirds of all crime in the UK is drug-related.
The Home Office says on its website that about three-quarters of crack and heroin users claim they commit crime to feed their habits.
PILOT SCHEME FINDINGS
Three-quarters reduced use of street heroin
Offences down from 1,731 in 30 days to 547 in six months
Spending on drugs down from £300 to £50 a week
Figures for group given heroin
Professor John Strang, who led the project, said the results were "very positive" because the scheme had helped cut crime and avoid "expensive" prison sentences.
Professor Strang, who is based at the National Addiction Centre, part of King's Health Partners, said the individuals on the programme were among those who had been the hardest to treat.
"It's as if each of them is an oil tanker heading for disaster and so the purpose of this trial is to see: 'Can you turn them around? Is it possible to avert disaster?'
"And the surprising finding - which is good for the individuals and good for society as well - is that you can," he said.