The cultivation of crops for making illegal drugs has declined steeply in both Afghanistan and Colombia, the world’s largest producers of heroin and cocaine, a UN survey shows.

The organisation’s 2009 World Drug Report , released yesterday, said that opium poppy cultivation fell 19 per cent in Afghanistan last year and coca leaf farming dropped 18 per cent in Colombia. The reductions reflect falls in the prices offered to farmers for their illicit crops, and stable or declining demand in the West. But the UN Office on Drugs and Crime said that it had identified a probable rise in the use and production of synthetic drugs, such as amphetamines, methamphetamines and Ecstasy, in the developing world.

The agency estimated that in 2007 up to 250 million people had used illicit drugs at least once in the previous year, but that drug consumption was concentrated among 18 million to 38 million “problem” users, or addicts.

Antonio Costa, the agency’s director, strongly rejected calls for the legalisation of illicit drugs. “Proponents of legalisation can’t have it both ways,” he said. “A free market for drugs would unleash a drug epidemic, while a regulated one would create a parallel criminal market. Legalisation is not a magic wand that would suppress both mafias and drug abuse. Societies should not have to choose between protecting public health or public security. They can, and should, do both.”

The UN figures showed substantial declines in drug production in Afghanistan, which produces 93 per cent of the world’s opium, and Colombia, which produces more than half the world’s cocaine. In Afghanistan, opium poppy cultivation was heavily concentrated in Helmand province in the south, where British troops are fighting the Taleban.

With more than 100,000 hectares (247,000 acres) of opium poppy cultivation, Helmand accounted for more than two thirds of the opium poppy grown in Afghanistan. The province also supplied more than half the 189,000-hectare total for the three main cultivating countries, Afghanistan, Burma and Laos. About 2,000 hectares on the Pakistani side of the Afghan border were planted with opium poppy. “Opium poppy cultivation continued to be associated with insecurity,” the report said. “Almost the entire opium poppy-cultivating area was located in regions characterised by high levels of insecurity.”

Prices for a kilogram of opium have fallen roughly half in Afghanistan, to about $75 (£46), in the past five years, though they have doubled in Burma.

In Colombia, coca leaf cultivation fell by 18 per cent, or 18,000 hectares, to 81,000 hectares, but production fell even more, by 28 per cent.

The United States, the world’s largest cocaine consumer, reported a significant drop in use, while in Western Europe, where consumption has surged in recent years, it has shown signs of stabilising.

“The $50 billion global cocaine market is undergoing seismic shifts,” Mr Costa said. “Purity levels and seizures in the main consumer countries are down, prices are up, and consumption patterns are in flux. This may help explain the gruesome upsurge of violence in countries like Mexico. In Central America, cartels are fighting for a shrinking market.”

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