Whale meat from Japan's processing ship Nisshin Maru is being illegally sold prior to the official government release of whale stocks, activists from the environmental group Greenpeace charged Thursday.

The sale of whale meat may only take place "once the International Whaling Commission meeting is finished in June," Sara Holden, a coordinator for the group, told a news conference in Tokyo. Greenpeace said it has obtained testimony from traders and bar owners that the meat from Japan's whale research missions is already being traded on the black market.

"Anything on the market prior to (June), from this year's expedition, is clearly, already illegal," Holden said at the Foreign Correspondents' Club of Japan in Tokyo.