Afghanistan's harvest of the raw material for opium is expected to be the largest on record this year, according to a UN report released Monday.

The United Nations Office on Drugs and Crime (UNODC) reported the sixth consecutive annual increase in poppy production since U.S.-led forces toppled the Taliban in 2001.

Afghan police are seen destroying opium poppies in April. The country's opium harvest is expected to the largest on record.
(Rafiq Maqbool/Associated Press)

The harvest has grown in size even though the international community has spent tens of millions of dollars to curb poppy cultivation. The total opium harvest will be 8,200 tonnes, up from 6,100 tonnes last year.

Afghanistan produced 93 per cent of the world's opium in 2007, up from 92 per cent last year, the report said, adding that international efforts to dissuade farmers from planting poppy crops in the southern provinces have been ineffective.

"The Afghan opium situation looks grim, but it is not yet hopeless," said UNODC executive director Antonio Maria Costa.

In the centre and north of Afghanistan, where the government has increased its authority and presence, opium cultivation is diminishing. The number of opium-free provinces more than doubled from six to 13, UNODC said.

Most production is in the south, where instability is much worse and NATO-led and Afghan government forces are battling the Taliban insurgency.

About 80 per cent of opium poppies were grown in a handful of provinces along the border with Pakistan in the south. In volatile Helmand province, where British troops are fighting the Taliban, opium cultivation rose 48 per cent to 102,770 hectares.