A prominent Chinese human rights activist has accused Beijing of breaking an agreement that secured his freedom.

Chen Guangcheng was at the centre of a diplomatic crisis between Beijing and Washington last year, when he escaped house arrest in April 2012 by scaling the walls of his home and taking a getaway car to the US embassy.

The blind activist had infuriated Chinese authorities by exposing forced adoptions in the country.

Beijing had allowed Mr Chen to leave for the United States following negotiations between the two nations.

But Mr Chen has accused China of violating its promise to ensure his family's safety and to investigate the past abuses.

He has voiced anger over a prison sentence handed down in November to his nephew, Chen Kegui, who was allegedly beaten in retaliation for the escape, which made headlines around the world.

"Not only has the Chinese government not fulfilled its own promises to me a year ago, but it has also become worse as they have not stopped persecuting my family members," Chen told AFP.

"This in itself shows that the Chinese communist regime has no intention to change its course," he said.

Chen is now calling on the United States to release the diplomatic records of last year's negotiations and to raise the agreement with China.

"The United States should make this clear publicly, demanding that the Chinese government fulfil its promises in the agreement with the US," Chen said.