The United Nations says opium production in Burma has increased for the fifth consecutive year.

In an annual survey published Thursday, the U.N. Office on Drugs and Crime said opium production rose by 5 percent in 2011.

The report also said the average price for opium jumped by nearly 50 percent in the past year, mainly because of strong international demand and a weakened national currency.

The U.N. says that poverty and a lack of food security continue to drive poor farmers to grow the lucrative crop, which is used to make heroin for the illegal drug trade.

Burma produced more than 90 percent of opium in Southeast Asia during 2011. It is the world's second largest producer of the crop, after Afghanistan.

The study also said political instability was a key factor in increased opium production. It said Shan State and Kachin State were most affected by the illegal drug trade. Both areas have witnessed years of conflict between Burmese authorities and ethnic rebels.

Earlier this year, the U.S. State Department named Burma as one of three countries that have “failed demonstrably” to fight illegal drug trafficking.

Western leaders have hoped that the country's new nominally civilian government will take tougher action to control the country's illegal drug trade.