The International Narcotics Control Board report says up to 50 percent of the medicines in developing countries are fake. It also warns that abuse of prescription drugs will soon overtake that of illegal narcotics worldwide.

The board said governments had to enforce existing laws and bring in new ones on illegal internet drug sales. Courier services, the general mail and local markets were other major means of counterfeit sales, it said.

The board's president Philip Emafo said: “Gains over the past years in international drug control may be seriously undermined by this ominous development if it remains unchecked. Instead of healing, fake drugs can take lives”.

The report said the UN and the World Health Organization (WHO) should help member states that do not have the resources to tackle the counterfeiters and traffickers.

The Vienna-based drugs watchdog also said prescription drug abuse had outstripped heroin, cocaine and Ecstasy in some parts of Europe, Africa and South Asia.

BBC