The National Association for the Care and Resettlement of Offenders (Nacro) says the number of people convicted or cautioned for drug offences has more than quadrupled in the past 10 years.

It says policies of imprisoning drug offenders have failed and it supports government attempts to concentrate more on treatment programmes.

But it is worried that access to the programmes is variable across the country and funding is often insecure.

Its report, Drug-driven crime: a factual and statistical analysis, found that people using cocaine and heroin were the most likely to commit crimes, including violent attacks which were linked to crack cocaine.

A study in the north west of England found that heroin addicts spent an average of £10,000 a year on drugs, with crack addicts spending twice as much.

The majority funded their habit partly or wholly by crime.

The cost of drug-related crime to victims is estimated to be as much as £2.5bn a year.

Jail 'ineffective'

In 1997/98, the government spent £1.4bn on drugs, with more than two thirds going to law and order and a third to treatment and prevention.

Nacro says jailing prisoners is an ineffective way of dealing with the problem.

A Home Office study of more than 7,000 offenders found that drug use was the most significant factor in reconviction rates - higher than employment, alcohol, finances and accommodation problems.

Heroin users can spend £10,000 a year on their habit

Nacro favours treatment over jail. It says a recent Department of Health study showed that drug use and crime dropped substantially during and after treatment. The number of offenders using drugs halved after two years and property crimes reduced by 68%.

The government has funded several pilot studies into treatment programmes, but results, although promising, are still in the early stages.

The Nacro report says research in the US revealed dramatic results for treatment programmes.

A 1996 study found that clients reduced drug use by about 50% in the year after treatment while the number of arrests fell by more than half.

Studies in the US and Australia suggest treatment is more effective if begun early and if it is carried out on a long-term basis.

The Nacro report says: "Past approaches, which have devoted the lion's share of resources for tackling illegal drugs to law enforcement and wholly inadequate funding to prevention and treatment, have failed.

"Getting drug dependent offenders into treatment programmes is by far the most effective option."

Nacro claims that for every £1 spent on treatment, £3 is saved on the crime bill.

However, it says current availability of drug treatment and rehabilitation services varies widely across the country.

Women fare worst

A recent survey for the Department of Health found that 64% of residential services and 61% of drug dependency clinics had a waiting list.

Other research found that agencies said they discouraged drug misusers from being referred for assessment because local authority criteria on eligibility was so strict.

Funding for projects treating women and the growing number of young users was particularly poor.

The government has pledged to increase investment in treatment of drug offenders and has set aside £217m for its 10-year drugs programme.

However, drug agencies say this will have to be divided between crime-fighting, education, prevention and other areas.