Some 25 to 50 percent of the medicines used in developing countries were now believed to be fake, the International Narcotics Control Board said in its 2006 report, quoting World Health Organisation (WHO) findings. Providers ranged from makeshift village markets to Web sites.

"This market is believed to be increasing rapidly. (It) exposes patients to serious health risks by providing access to poorly or incorrectly labelled medicines that are ineffective, substandard and, in some cases, even lethal," it said.

The board spotlighted dangers inherent in graft-ridden, weakly-regulated markets, where bogus medicines had proliferated, and the widespread and growing misuse of prescription and weight-loss drugs.

The annual report also said Iranians had become the world's highest per capita abusers of opiates as they straddled export corridors from lawless Afghanistan, source of more than 90 percent of the opium produced globally.

The Vienna-based board is an independent judicial body elected by United Nations members to monitor the implementation of world drug control conventions.

Separately, the board denied accusations from rights groups that it was hampering efforts to prevent the spread of AIDS. It said it supported exchanges of sterile syringes for drug addicts but not what it called poorly supervised "drug injection rooms" because these only encouraged trade in illegal narcotics.

INTERNET TRAFFICKING

In order to meet the growing demand for cheap medicines, drug traffickers have increasingly turned to the Internet, postal and courier services to distribute their ersatz wares.

"The abuse and trafficking of prescription drugs is set to exceed abuse of illicit drugs. Demand for these products is so high that it has given rise to a new problem -- counterfeit products ... Progress made over the last 40 years in the control of illicit drugs is now being undermined," the report said.

Board president Philip Emafo said governments needed to enforce existing laws and rethink how to tackle Web crime.

The report said the UN Office on Drugs and Crime and WHO should help member states that have little financial means and are overwhelmed by traffickers able to evade or buy off poorly-paid and equipped police forces.

Emafo, a Nigerian, said Iran had developed the highest rate of opiate abuse because it was the "unfortunate" first conduit point for opium pouring out of Afghanistan towards Europe.

"In the process of being trans-shipped, drugs are deposited along the route," he said. "It is possible that because of the Iranian government's enforcement activity, the drugs come in, but (some) are not able to go out."

Human rights groups have accused the board of promoting policies that ignore AIDS prevention and other public health issues, for example by discrediting programmes such as the use of methadone for treating addicts.

"Safe-injection facilities ... around the world ... reduce practices leading to HIV and hepatitis transmission, steer people to treatment for their addictions, and prevent death from drug overdose," said Joanne Csete, the director of Canada's HIV/AIDS Legal Network on Thursday.

Emafo said the criticism was "misplaced and wrong".