The London- and Washington DC- based Environmental Investigation Agency called in a report for both governments to stop the trade, which is worth hundreds of millions of dollars a year and supplies China's furniture industry.
EIA says Chinese businesses acquire the rights to illegally log Burmese mountains through bribery.
EIA campaigner Julian Newman says the volume of illegal timber crossing the border has risen to nearly 900,000 cubic meters a year not far off the 2005 peak of about 1 million cubic meters, which fell after Chinese authorities temporarily clamped down.