BEIJING (Reuters) - China's ruling Communist Party is having to fight back against a flood of online information casting doubt over, distorting or slandering the party's official history, a senior official said on Wednesday (July 6).

Party history is a sensitive subject in China as so much of the party's legitimacy rests on its position as claiming great historical achievements, such as leading China to victory over Japan before and during World War Two.

Dissenting views, such as historians pointing out much of the fighting against the Japanese was done by the then-Nationalist government, are generally not welcomed.

More painful topics, like the chaos of the Cultural Revolution or the Great Leap Forward, remain largely taboo.

The party refers to those who stray from its line as practising "historical nihilism".

Zhang Shujun, deputy head of Party History Research Centre, said the greatest harm this caused was making people doubt the party's leadership.

"Our attitude is very clear when it comes to historical nihilism, and that is to have a clear-cut stance on opposing it, to oppose any mistaken point of view or tendency on party history," Zhang told a news conference, according to an official transcript.

The Internet is the "main battleground" for this problem, he said. "At present there's just too much of this information on the Internet," Zhang added. "We need to set forth the facts and discuss them rationally."

He gave an example of one story he said had circulated on the Internet saying Mao Zedong, the founder of modern China, did not write most of which was attributed to him and had it ghostwritten instead.

The party effectively batted away that story, drafting in the help of "old comrades" who look after the Mao archives to persuade the public, Zhang said.

"The focus is to collect and evaluate the wrong points of view and tendencies on the internet that distort party history and rebut them."