China must not rely on whistle-blowing mistresses to expose corrupt officials, China's top newspaper said today, after a string of such incidents led to some people hailing the girlfriends as graft-busters.

President Xi Jinping has singled out corruption as a threat to the Communist Party's survival, and the keeping of mistresses in lavish apartments, which breaks party rules, has come to represent to many people the excesses of power in China.

In a recent high-profile case, Liu Tienan, once the deputy chief of China's top planning agency, was sacked after his mistress told a journalist that Liu had helped defraud banks of $200 million, state media reported.

But the People's Daily, the ruling Communist Party's official newspaper, questioned the woman's motives and said China could not rely on such people to fight corruption.

"Even though at times, for many reasons, mistresses are led by fallings out with corrupt officials to denounce them, at the root of the issue, both their motives are the same - to satisfy each other's greed," the newspaper said in an editorial.

"Some directly solicit bribes or seek huge illegal profits. To pin anti-corruption hopes on them is to go in for evil attacking evil," it said. "It is not the right path for the will of the people."

The paper noted another case in which a tape that showed a district party chief having sex with his mistress went viral on Weibo, China's version of Twitter. The official, Lei Zhengfu, was sacked, along with several others in the city of Chongqing.

His mistress, 24-year-old Zhao Hongxia, was charged with extortion this month for her alleged part in a criminal ring that blackmailed officials by secretly filming sex sessions.

Zhao has become something of a national anti-hero, eliciting condemnation from those who called her behaviour immoral even as others commended her for her hand in bringing down Lei.

The People's Daily editorial was met with scepticism by some Weibo users who joked that mistresses were the real heroes in the fight against graft.

"In this very special country, mistresses make a bigger contribution to anti-corruption than so-called public security authorities," said one user, who used the moniker "Xie Peng is Xie Peng."

"Without them, who can we depend on?" a user called LastDay1981 asked.

"Quit griping," the poster said, referring to those responsible for the newspaper editorial.