internet firms criticised for their business dealings in China are agreeing to guidelines on what data they should share with authorities.

The new guidelines call for Google, Yahoo and Microsoft to try to reduce the scope of government requests that conflict with free speech and other human rights principles. They also require companies to seek requests in writing, along with the names and titles of authorising officers.

The Global Network Initiative guidelines, drawn up by the firms along with human rights groups, investors and academics, are less about "what happens when you get a knock on the door than what are you doing before then", said Leslie Harris, of the Centre for Democracy and Technology.

It was not clear, however, what practices will change, as many key points are open to interpretation.

"What's disappointing is that the amount of effort didn't produce something more substantial," said Morton Sklar of the World Organisation for Human Rights USA, which sued Yahoo for giving Chinese officials information that led to the arrest of two journalists.

Google has come under fire for censoring about 2% of its search results in China.