China is using the 2008 Olympic Games as a catalyst for suppressing dissent in the name of stability, Amnesty International has said.
China vowed to improve human rights in its bid for the Games
A report by the group welcomed some reforms, but criticised China's detentions without trial and tightened control of the media and the internet.
Amnesty said China had failed to keep its promise to improve human rights in the lead up to the Games.
Chinese authorities have not yet commented on the report.
The report said the August 2008 Olympics was "a catalyst for a continued crackdown on human rights defenders, including prominent rights defence lawyers and those attempting to report on human rights violations".
It also said there were fears that "abusive systems", such as the ability to jail a crime suspect for up to four years without trial, were being used to detain petty criminals, vagrants and drugs addicts in an effort to "clean up" Beijing for the Games.
Amnesty has welcomed the country's reform of death penalty laws and allowing foreign journalists greater freedoms, but said they were overshadowed by a hardline crackdown of peaceful dissent.
It has called for the International Olympic Committee (IOC) to raise the human rights issue with Chinese authorities.
"The IOC cannot want an Olympics that is tainted with human rights abuses - whether families forcibly evicted from their homes to make way for sports arenas or growing numbers of peaceful activists held under house arrest," Catherine Baber, Amnesty's deputy Asia-Pacific director, said.
But the IOC executive board has said it is a sports organisation and does not have a political role.
Previously, China has dismissed Amnesty reports, saying it is fulfilling all the commitments it made over human rights in its quest for the Games.
During bidding in 2001, the Beijing committee pledged that a win for China would help promote the development of human rights in the country.