Drug addicts receiving treatment should be given shopping vouchers to encourage them to kick their habit, an NHS body has suggested.
The National Institute for Health and Clinical Excellence accepts the idea for England and Wales is controversial.
But evidence from international trials shows modest financial incentives can cut drug abuse by hardened addicts.
Users could get vouchers worth up to £10 at NHS treatment programmes - if tests show they are free of drugs.
NICE says the idea would be cost-effective, and there would be a public health benefit because addicts could also be screened for infectious diseases - such as HIV and tuberculosis.
The proposal for an incentive scheme is contained in draft guidance on how the NHS in England and Wales should handle drug misuse.
Debates about how NHS money should be spent have intensified in recent years.
NICE will soon face its first legal challenge when groups angry about restrictions on drugs for Alzheimer's Disease challenge its processes.
Could help many
Mr Stephen Pilling, a consultant clinical psychologist from University College London, who advised the NICE group, estimates 50,000 addicts in England and Wales could take part in the scheme.
He believes it could help up to half of them stay off drugs.
He said: "I think the group, having thought it through carefully, have firmly come to the view that it provides a much better and positive way to relate to drug users than sometimes we have done in the past.
"I don't think it's bribery - I think it's an effective treatment that brings real benefit. We are convinced it is a proper way to deal with people."
Mr Pilling said the key was that the system provided an incentive for people to present a clean drug test.
"There will be some big challenges in spelling out the benefits to NHS staff and monitoring the implementation of this.
"But the evidence shows small incentives can have a marked impact."
The NICE group looked at evidence from more than 20 trials, mainly done in the US.
The results convinced the group that incentive schemes worked and were cost-effective.
Studies have shown many people with drug problems respond much better to positive incentives than to programmes which focus on punishment and make them feel guilty.
Some of the American trials involved giving drug addicts vouchers for burger chains, but Mr Pilling said that wouldn't be the case in the NHS.
He said: "A clear purpose of the use of vouchers would be to promote a healthy lifestyle - we would want to encourage them to buy appropriate food or improve their leisure activities."
Richard Phillips, director of services at Phoenix Futures - drug and alcohol treatment specialists - said providing incentives to people receiving treatments could be controversial.
But he said: "If it works to keep people in treatment there would be considerable benefits to the public.
"The cost of a few sandwiches is a small price to pay if it keeps more drug users on the path of recovery and off illegal drugs."
But Mike Trace, chief executive of the Rehabilitation of Addicted Prisoners Trust cast doubt on whether the concept would work.
He told the BBC Radio Four Today programme: "If you just rely on rewards for abstinence and you're not treating people's complex problems, you're not going to change the behaviour."
Linda, whose son Neil used heroin and crack cocaine for 15 years, said faster access to treatment is more important than vouchers.
"I'd rather money was spent on drug treatment centres, where people could be helped immediately.
"These young people have deep-seated problems - that's what needs to be addressed.
"That's where the money should go - not giving them vouchers for food, clothes or shopping."
Professor Peter Littlejohns, NICE's clinical and public health director, said the aim of the new guidance would be to offer a package of interventions to provide support for people trying to beat their addiction.
The draft guidelines also consider how to give addicts information about self-help groups, such as Narcotics Anonymous, and how to best support families and carers.
A consultation on the proposals is open until early March, with full guidance due to be issued to the NHS in the summer.
The Department of Health said its drug treatment budget was to increase from £375m to £388m for 2007/8. It will also input £10m of capital funding.
A spokesman said it would be responding to the NICE consultation.
He added: "NICE's current draft guideline makes a number of recommendations on the use of suitable privileges or rewards to encourage compliance with treatment regimes.
"This is one of a range of approaches that may support better outcomes."
so i get hooked on drugs... go to my GP... get clean... go to check ups and each time i come up clean i get vouchers... tesco, boots HMV here i come...