The union representing journalists in the UK and Ireland called on its 40,000 members to boycott all Yahoo Inc. (YHOO) products and services to protest the Internet company's reported actions in China.
The National Union of Journalists said it sent a letter on Friday to Dominique Vidal, Yahoo Europe's vice president, denouncing the company for allegedly providing information to Chinese authorities about journalists.
The union also said it would stop using all Yahoo-operated services.
Yahoo has been cited in court decisions as supplying China's government with information to help them identify, prosecute and jail writers advocating democracy.
"The NUJ regards Yahoo!'s actions as a completely unacceptable endorsement of the Chinese authorities," wrote Jemima Kiss, chairman of the NUJ new media council in the letter to Vidal.
Yahoo! spokesperson Mary Osako said the Sunnyvale, California-based company believes it must conduct business in each country in ways that comply with local laws.
"Let us make clear that we condemn punishment of any activity internationally recognized as free expression, whether that punishment takes place in China or anywhere else in the world," Osako said in a statement e-mailed to Reuters.
Yahoo Chairman and Chief Executive Terry Semel told investors at the company's annual shareholder meeting last week that the company had no choice but to comply with local laws and did not have the power to change Chinese policy alone.
He has repeatedly called on the Internet industry to band together to address the issues of free expression at stake in the controversy and asked the U.S. government to urge China to encourage greater media freedom.
The company has been accused by the NUJ and other journalism groups of providing records that led to an eight-year prison term for Li Zhi for discussing pro-democracy issues in a Web forum and of helping to identify Shi Tao, who was sentenced to prison for 10 years for forwarding a government e-mail to the foreign press.
Kiss said the NUJ was advising all members, who include reporters, editors, photographers and illustrators, to boycott Yahoo until the company "changes its irresponsible and unethical policy."
Other Internet companies also have come under fire lately for some actions in China, including Google Inc. (GOOG) for saying it would block politically sensitive terms on its Web site in the country and Microsoft Corp.'s (MSFT) MSN for shutting down a blog under Chinese government orders.