A leading Chinese advocate of internet freedoms has issued a scathing denunciation of the US portal Yahoo for its role in helping Communist authorities to prosecute an independent-minded local journalist, jailed for 10 years for “leaking state secrets”. Veteran dissident Liu Xiaobo, in an open letter to Yahoo co-founder Jerry Yang, accuses the US company of betraying its customers and supporting dictatorship by providing information on journalist Shi Tao to Chinese authorities. “Major foreign companies should not be helping the Chinese government to limit freedom of speech on the internet,” Mr Liu told the Financial Times. “This is shameless.” Yahoo on Monday refused to comment on the contents of the letter. A company spokeswoman at its base in Silicon Valley said it only released information to the authorities “when legally compelled to do so, and then only in a way that complies with both local laws and our privacy policy”...Google has excluded sites blocked by the state from its Chinese news service, while MSN [Microsoft] banned the words “freedom” and “democracy” from parts of its new Chinese website. In his letter, Mr Liu calls on internet users to boycott Yahoo services until the company apologises to Mr Shi, compensates his family and “ceases close co-operation” with China's censors.