An international survey has found that illicit drugs are now generally cheaper and purer than at any time in the last 20 years.
A report by the International Centre for Science in Drug Policy, published in the British Medical Journal Open, looked at data from seven international government-funded drug surveillance systems.
Researchers said it was time to consider drug use a public health issue rather than a criminal justice issue.
The BBC reports seven drug surveillance systems the study looked at had at least 10 years of information on the price and purity of cannabis, cocaine and opiates, including heroin.
The report said street prices of drugs had fallen in real terms between 1990 and 2010, while their purity and potency had increased.
The report also found there had been a substantial increase in most parts of the world in the amount of cocaine, heroin and cannabis seized by law enforcement agencies since 1990.
Most national drug control strategies have focused on law enforcement to curb supply despite calls to explore other approaches, such as decriminalisation and strict legal regulation. It concluded:
"These findings suggest that expanding efforts at controlling the global illegal drug market through law enforcement are failing."