A retired doctor who exposed China's Sars cover-up has called on the ruling Communist Party to admit its mistakes handling the 1989 Tiananmen protests.
Dr Jiang's outspoken stance on Sars won him public backing
Jiang Yanyong, who treated people for gunshot wounds after the protests were brutally suppressed, issued the call in a letter to China's parliament.
"The mistake made by our party should be resolved by the party itself," the letter said.
Hundreds of unarmed protesters were killed during the crackdown.
The incident, which is still so sensitive it is dangerous to raise publicly, is also believed to be a source of serious disagreement within the Communist Party, suggesting Dr Jiang's call will be ignored.
Nevertheless, it will come as a major embarrassment to the party, especially since the country's National People's Congress is gathered in Beijing for its annual meeting.
"The new leaders of the party and the country ... should re-examine June 4," said the letter, copies of which were obtained by several media outlets.
"Our party should rely on itself to settle the mistakes it has committed. The earlier and the more thoroughly it settles the mistakes, the better," it said.
Mr Jiang cited former President Yang Shangkun as telling him that "the June 4 incident is the most serious mistake committed by our party in history."
The doctor became a household name in China last year when he contradicted government figures for the spread of the deadly Sars virus in the country, revealing that an official cover-up was taking place.
He was a surgeon at Beijing's No 301 Hospital during the 1989 protests, which called on China's leaders to speed democratic reform.
He described in his letter how he and his colleagues fought frantically to save patients as they arrived riddled with bullets.