BEIJING • China's top graft-buster launched a scathing attack on the ruling Communist Party's members yesterday, writing that party political culture remained "unhealthy" and governance weak even after five years of renewed effort to fight the problem.

The comments by Mr Wang Qishan, who runs the party's anti-corruption watchdog, came after sources said a senior official who was considered a contender for promotion at this autumn's key party congress is being investigated for "discipline violations".

Mr Wang said the anti-graft inspections that started after President Xi Jinping took office five years ago have routinely discovered the same problems.

"All of the issues discovered during the inspections reflect the weakening of party leadership, shortcomings in party building and insufficient efforts to strictly enforce party discipline," Mr Wang wrote in the party's official People's Daily.

"Party concepts are faint, organisation is lax and discipline flabby. The root is in the party's internal political life being not serious, and unhealthy," he said.

As head of the Central Commission for Discipline Inspection (CCDI), Mr Wang has been the chief enforcer of Mr Xi's pervasive anti-corruption drive and is widely considered as the party's most powerful man after Mr Xi.

Despite an unwritten retirement age rule suggesting that he should step down at this autumn's party congress, Mr Wang, who turns 69 this month, could be kept on by Mr Xi as head of a new National Supervisory Commission that will combine the powers of several graft- fighting bodies, sources with ties to the leadership have told Reuters.

Mr Wang said in his People's Daily piece that the fight against graft would be "a long process".

Critics of Mr Xi's anti-graft campaign have long accused it of being a tool to sideline political rivals.

Mr Sun Zhengcai, the Chongqing party boss abruptly removed from office last Saturday, had been seen as a potential candidate for elevation at the autumn congress and as a possible future premier.

However, his star had waned since coming under criticism from the anti-corruption watchdog. The government has yet to say what has happened to him.

Sources with ties to the leadership and foreign diplomats say Mr Sun has been out of favour since the CCDI criticised the Chongqing authorities in February for not doing enough to root out lingering "poisonous" influence from disgraced former party boss Bo Xilai.

Bo was once himself a contender for the top leadership before being jailed for life in 2013 in a dramatic corruption scandal.

Mr Xi's crackdown on corruption has seen dozens of senior officials jailed. Mr Xi has warned, like others before him, that the problem is so serious it could affect the party's grip on power.

Mr Wang agreed with that assessment in his article. "The greatest challenge to our party ruling for a long time and ruling fully is effective supervision," he wrote.

Exposing problems shows the party's confidence in facing them, Mr Wang said. "Putting out there the problems that objectively exist shows a high level of self-confidence and staunch focus, winning over the faith, trust and confidence of the people in the party's centre."

The crackdown has not just been focused on issues such as bribery and use of public money to fund lavish lifestyles. It has also taken aim at those whose political loyalty is found lacking or who publicly express doubt about party policies.

Mr Wang said some party members practised "political nihilism", casting aside their beliefs, while others were guilty of "phoney politics", seeing the word of the leadership as nothing more than slogans.

The party has long said it alone can deal with corruption, dismissing any calls for an independent body separate from the party to tackle the issue.

REUTERS