The UNODC said in an annual forecast on opium production in Afghanistan that insecurity and a general lack of agricultural assistance was responsible for substantial increases of opium cultivation in the country.
The report said there was a strong link between cultivation of poppy, a raw material for heroin production, and security in Afghanistan.
"Villages with a low level of security and those which had not received agricultural assistance in the previous year were significantly more likely to grow poppy in 2013 than villages with good security and those, which had received assistance," the report stated.
The U.N. report said production is gaining momentum in most areas of the country, even in regions where poppy cultivation was once stopped.
Helmand farmer Hamidullah -- many Afghans use only one name -- told the BBC that it was tough making a living on alternative crops like cotton.
"The price of cotton is very low," he said. "It does not cover the cost of production."
The BBC reports the UNODC assessment is a reflection of the international mission in Afghanistan. In Helmand, where British forces were based, opium production last year was three times as high as when it was when deployment began in 2006.