Yahoo has been accused for a third time of handing over the details of a Chinese user to the authorities.

A report from Reporters without Borders alleges that the company provided the details of a pro-democracy activist using its email service to the Chinese authorities.

Jiang Lijun, 40, was sentenced to four years in prison for "subversion" on 18 November 2003, accused of seeking to use "violent means" to impose democracy. 

A court docket (Chinese language PDF) obtained by Reporters without Borders alleges that the conviction was secured with the help of information provided by Yahoo Hong Kong. 

According to the verdict, Yahoo Hong Kong confirmed that the email account 'ZYMZd2002' had been used jointly by Jiang Lijun and another pro-democracy activist, Li Yibing.

"Little by little we are piecing together the evidence for what we have long suspected: that Yahoo is implicated in the arrest of most of the people that we have been defending," the press freedom organisation said.

"Last week we went to the headquarters of the company to urge them to end this collaboration. We called on them to remove their email servers from China, because it is the only way to avoid taking part in the current crackdown against journalists and democrats."

The case follows that of Li Zhi, a 35 year-old civil servant who was allegedly identified by Yahoo and sentenced to eight years in jail for "inciting subversion" after criticising local corruption in his district. 

Last year Yahoo was accused of giving information to Beijing which led to the imprisonment of reporter Shi Tao, who was sentenced to 10 years in jail in April 2005.

Yahoo was unavailable for comment at time of going to press.