COCAINE and heroin addicts on a government treatment programme are being given extra drugs as a reward for good behaviour, it has been claimed.

A survey of almost 200 clinics in England by the National Treatment Agency (NTA), found users were being offered extra heroin substitute methadone or anti-depressants for clean urine samples.

The NTA said the practice was unethical and it wanted to see certain practices `squeezed out of the system'. A third of clinics in the survey said users who produced a drug-free urine sample may be offered increased doses of heroin substitute as a reward - known as `contingency management'.

A quarter admitted that clients can choose the type of substitute drugs they want.

The survey also found clinicians offering anti-depressants, cash vouchers or access to detox as a reward.

The NTA, which runs the £500m-a-year treatment scheme, said offering drugs for anything other than clinical need was wrong.

The agency's chief executive Paul Hayes said: "Giving extra drugs as a reward isn't a practice we would advocate.

"One of the things that's important before we start rewarding people through things like contingency management is to make sure that we're doing it according to the best principles for drug treatment.

"There are a range of practices associated with drug misuse that are not what we would want them to be."

Mr Hayes said the NTA was set up not only to expand the provision of drug treatment, but also to improve its quality.

While he says it is appropriate for other drugs to be prescribed alongside prescription drugs to help deal with the withdrawal symptoms, they should not be given as a reward and the agency `wouldn't advocate' such a practice.

He said doses of drugs should be determined by an individual's needs and not by whether or not they were co-operating with the programme.