Drug addicts are being prescribed heroin on the NHS across London, a BBC investigation has revealed.
There has been a long-running public debate about whether addicts should be widely offered the drug.
Supporters say prescribing diamorphine - pure heroin - stops them committing crime to feed their habit.
They argue a regular supply of pure heroin means addicts can build a stable life and find employment.
In January, Health Minister Anne Milton told Parliament: "The Drugs Strategy sets out the coalition government's commitment to continue to examine the role of diamorphine prescribing for the small number who may benefit.
"We will set out plans in due course."
But the BBC has used Freedom of Information requests to all of London's primary care trusts to establish that heroin is already being prescribed across the city - and not just in medical trials.
In exceptional cases, doctors can already gain special approval from the Home Office to issue heroin to addicts.
In the past three years almost 120 addicts have been provided with heroin in this way in London and it was prescribed in 10 of the city's 32 boroughs.
The BBC has learned doctors even have the power to prescribe cocaine, although this is rare.
Some people said they were disappointed with the news.
Former Conservative frontbencher Ann Widdecombe said: "My concern about giving heroin to addicts is you are not tackling the root cause of their problems.
"You don't get someone off drugs by giving them drugs.
"You remove the danger of dirty needles - but not the addiction."
'Costs huge amounts'
Dr Adrian Rogers, a retired GP, said he believed an addict's addiction should never be maintained "in any shape or form".
"The only thing you should offer is detoxification," he said.
"Drugs prevention has grown into a massive industry - costing the taxpayer huge amounts."
He added: "I feel terribly sorry for addicts, but I don't believe they should have drugs provided by the taxpayer."
It costs the NHS about £14,000 to maintain an addict on heroin for a year.
Supporters of heroin prescription say this is dwarfed by the cost of crime users might otherwise commit. Experts have estimated an addict spends £45,000-a-year on average on street heroin.
In 2000, Pauline Holcroft's daughter Rachel Whitear died at the age of 21 from a heroin overdose.
The case hit the headlines when her parents released photographs of the dead student to warn others.
Mrs Holcroft said she "had no idea" that heroin was being prescribed to addicts.
She said: "I thought they could only prescribe methadone.
"It seems to me this has been kept quiet.
"When Rachel's case became public we went to see see clinics [shooting galleries] in Amsterdam - I didn't think it happened here too."
Mrs Holcroft said she supported the idea.
She said: "If my daughter had to use heroin I'd have preferred it in hospital, supervised properly along with a programme to get her off it. I can only see it as helpful.
"Methadone [the most common heroin substitute] does not seem to help.
"In many cases people prescribed methadone go and buy heroin anyway."
Mrs Holcroft added: "I wish Rachel had been given that opportunity."
Addicts prescribed heroin must take it under medical supervision several times a day.
The BBC asked every NHS primary care trust in London to reveal how many of the addicts taking prescribed heroin became drug-free, compared to those taking methadone.
Almost all of the bodies claimed this was impossible because of the way the figures are recorded.
But Brent Shared Care Prescribing Team, which treats addicts in the boroughs of Brent, Westminster, Hammersmith, Barnet, Kensington and Chelsea, Ealing, Harrow, Camden and Islington, did reply fully.
In the last three years it prescribed 466 addicts with methadone. Six were discharged drug-free, a success rate of 1.2%.
'Focus on recovery'
Over the same period, 48 people were issued with heroin. Six kicked the habit - a 12.5% success rate.
NHS North West London, which presides over the team, refused to comment.
Dr Costas Agath, a Westminster-based practitioner who prescribes heroin to addicts, said: "When people withdraw from heroin they're in a very bad state.
"They sweat, throw up, have muscle cramps and diarrhoea - the last thing they can do is focus on recovery.
"The medication helps them regain control over their body."
He continued: "If people don't have these symptoms they can see the way forward more clearly.
"They see the importance of good relationships or employment.
"It helps them realise life is not just about drugs - it's about a sunny day, lying in the grass with someone you love."
The charity DrugScope said prescribing heroin was useful in serious cases.
Chief executive Martin Barnes said: "It can stabilise someone's drug use, achieve positive health outcomes and reduce crime.
"It can put someone on the path to becoming drug-free."
He added: "This is not a heroin free-for-all."
The Department of Health said its position had not changed since the minister's January statement.