Afghan President Hamid Karzai is accused of being reluctant to move against political allies who profit from the opium trade. (CBC)

Afghanistan's President Hamid Karzai is protecting narcotics traffickers in his country and impeding U.S. efforts to stop opium poppy cultivation in the provinces of Kandahar and Helmand, a former U.S. state department official says.

In an article on the New York Times website, Thomas Schweich says Karzai is reluctant to move against political allies who profit from the opium trade, even though the Taliban insurgency in southern Afghanistan is partly funded by poppy cultivation.

"Narco-corruption goes to the top of the Afghan government," he writes.

Until last month, Schweich was the State Department's co-ordinator of counter-narcotics and justice reform in Afghanistan. His article is the strongest accusation yet from an insider of links between Karzai's government and the booming Afghan opium trade.

"Karzai was playing us like a fiddle," Schweich writes. "The U.S. would spend billions of dollars on infrastructure development; the U.S. and its allies would fight the Taliban; Karzai's friends could get richer off the drug trade."

Speaking in Kabul, Karzai strongly rejected Schweich's accusations.

The booming opium trade was a mark of how poor Afghans were, Karzai said, and most narcotics traffickers were foreigners who were exploiting poor Afghan farmers.

"Without doubt, some Afghans are drugs smugglers, but [the] majority of [smugglers] are the international mafia who do not live in Afghanistan," he said.

Karzai said his government had put hundreds of traffickers behind bars and would continue to do so.

Allies lack united stance on Afghan opium

Schweich also says high-ranking officials in the Pentagon, some U.S. field commanders in Afghanistan and American allies in combat operations in the country oppose aggressive counter-narcotics measures, and this benefits corrupt Afghan officials.

He singles out Britain, which has most of its troops deployed in Helmand, as being most opposed to military-style poppy eradication, and says a British general based in Washington and senior Pentagon officials helped scupper plans to step up anti-narcotics efforts in Afghanistan.

“Defence Department officials were thus enlisting a foreign government to help kill U.S. policy,” Schweich writes.

Karzai, the former official says, takes advantage of this lack of unity in Washington and among its European allies to go softly on drug traffickers in his government and even within his own family in Kandahar.

In his New York Times article, Schweich says many of Afghanistan’s 34 provinces have successfully discouraged poppy cultivation, but the crop is now concentrated in the south.

"The north and east … continued to improve because of strong political will and better civilian military co-operation,” he writes, “but the base of the Karzai government — Kandahar and Helmand — would have record crops, less eradication and fewer arrests than in years past. And the Taliban would get stronger."

U.S. supports Karzai

Responding to the article, a State Department spokesman, Gonzalo Gallegos said Washington was a firm supporter of Karzai and believed he was sincere in fighting corruption and the narcotics trade.

"We know and understand that there is a corruption issue in Afghanistan but we're working with the sovereign government," Gallegos said Thursday. "President Karzai has shown us through word and deed that he is working with us to help improve the plight of that country."

Opium poppy production has soared since the U.S.-led invasion of Afghanistan in 2001 toppled the Taliban government in Kabul.

In their latter years in power the Taliban had banned the cultivation of opium poppies, but within five years of the invasion, Afghanistan’s farmers were growing record crops.

The United Nations estimates that just under 9,000 tonnes of opium came from Afghanistan's poppy fields in 2007, with a street value of about $4 billion.

With files from the Associated Press