HONG KONG (AFP) - The publisher of a memoir by deposed Chinese leader Zhao Ziyang defended the book following an attack by Beijing-backed media that made a rare mention of the 1989 democracy protests.

Zhao was ousted over his sympathy with the Tiananmen Square protests in Beijing which were crushed by army on June 4, 1989 with the deaths of hundreds, possibly thousands.

Bao Pu, the publisher of the Chinese version of the book and the son of a former top Zhao aide, said the "Prisoner of the State" was a crucial effort to overturn Beijing's official condemnation of the protests.

"The main objective to publish this memoir is the correction of history," the Hong Kong-based Bao told AFP.

"We believe this publication will fill the vacuum of a part of history that is missing."

His comments came after several Beijing-backed newspapers published in Hong Kong said in a lengthy commentary that the memoirs -- and western media who promoted them -- were trying to foist democracy on China.

"If overturning the verdict on the 1989 political turbulence is the interim objective of the 'memoirs' editor and those foreign media promoting the book, then advocating the change of China's current political system into Western parliamentary democracy is their ultimate goal," said the commentary, signed by "Qi Lin" and published Wednesday.

The commentary said overturning the government's official verdict on protests would incite social upheaval and could even lead to a "global calamity".

The article was published in the English-language China Daily, but did not appear in the mainland edition.

Any mention of the protests or the subsequent deadly crackdown is very rare in Chinese state media.

The book, which was released in English this month, was based on recordings by Zhao recorded before his death in 2005 while he was held under house arrest following his removal from the head of the Communist Party.

He was ousted after refusing to authorise the use of the military to end six weeks of unprecedented pro-democracy rallies in Tiananmen Square in the spring of 1989.

The memoir recounts Zhao's opposition to hardliners and his failed efforts to persuade leader Deng Xiaoping not to use force to quell the protests.

China is tightening curbs on key dissidents before next week's sensitive 20th anniversary of the crackdown, activists and their relatives have said.