Worldwide, 70 percent of soy, 46 percent of cotton and 24 percent of corn are genetically modified.

Due to concerns over consumer rights, at least 35 countries and regions including China, Australia, the EU, Japan and Indonesia have adopted mandatory labeling for any product that has been genetically modified.

China's labeling regulation stipulates that all products containing GM ingredients including seeds, animal feed and food should be labeled under the framework of the Biosafety Regulation of GMOs in Agriculture, first announced in June 2001 by the Ministry of Agriculture.

"The regulation, however, is poorly enforced as many GM products are sold without labeling at all," Jiang said.

"A lack of strict management and the absence of a monitoring mechanism is largely to blame," he acknowledged.

Other reasons include the lack of a cost-effective method for detecting GM products with sufficient sensitivity, coupled with business concerns that labeling would result in lower competitiveness, said Professor Wang Canfa of the China University of Political Science and Law.

"Given that GM products like soybean oil, papaya, tomatoes, potatoes and tobacco are now widespread in China, the labeling rule, which is about consumer choice and rights, should be forcefully and strictly implemented," he said.

He also called on the government to further regulate GM labeling, including having these details prominently displayed on packaging, so consumers could choose whether to buy those items.