Yahoo's general counsel and executive vice president has apologised for unintentionally misleading statements regarding his company's activities in China.

Michael Callahan had denied in earlier testimony to the US Congress that Yahoo had received details of the activities of Chinese activist Shi Tao before handing over information about him to the police.

It has since emerged that the charges against the activist of "illegally providing state secrets to foreign entities" were known to Yahoo.

"Months after I testified before two House subcommittees on Yahoo's approach to business in China, I realised that Yahoo had additional information about a 2004 order issued by the Chinese government seeking information about a Yahoo China user," Callahan said in the statement.

"I neglected to directly alert the committee of this new information and that oversight led to a misunderstanding that I deeply regret and have apologised to the committee for creating."

The existence of the charges was made public after documents were released by San Francisco-based human rights group The Dui Hua Foundation.

"This new documentation suggests that Yahoo's Beijing office was at least aware of the general nature of the crime being investigated in the Shi Tao case, " said Joshua Rosenzweig, manager of research and publications at The Dui Hua Foundation.

"Even if Yahoo was unaware of the specific circumstances, or the name of the individual involved, one does not have to be an expert in Chinese law to know that 'state secrets' charges have often been used to punish political dissent in China.

"We must remember that before Shi Tao there were three other Chinese dissidents about whom Chinese police obtained user information from Yahoo in Beijing."

Shi Tao was sentenced to 10 years in jail in 2005 following Yahoo's release of the information. The company is currently being sued for its actions by the World Organization for Human Rights USA.

Yahoo has been heavily criticised by human rights organisations for its activities in China and its willingness to censor information or work with authorities in countries where dissent is not allowed.

The company has been accused of handing over details that have led to the jailing of three people who criticised the Chinese government online.