The commission said its investigation of the ministry which controls millions of policemen and domestic security agents, has not “made enough effort to eliminate the poisonous influence of Zhou Yongkang, [former Interpol head] Meng Hongwei and [ex-deputy minister for public security] Sun Lijun and not enough supervision and control over executive power in key areas and processes.”

Zhou, the former head of the Central and Political Legal Affairs Commission, the country’s top law enforcement agency, was jailed for life in 2015 for taking bribes, abusing power and leaking state secrets.

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Meng, whose disappearance on a return visit to China from Interpol’s headquarters in France made headlines around the world, was jailed for 13 and a half years in January last year. His former colleague Sun, who has not yet appeared in court, was placed under investigation in April.

The current public security minister Zhao Kezhi promised that the ministry would learn from the “serious discipline and law violations of Meng Hongwei, Sun Lijun and others [and] resolutely and thoroughly eliminate their toxic influence”.

The CCDI also said that Shaanxi province had not done enough to root out the “poisons left” by former party chief Zhao Zhengyong, who was given a suspended death sentence for bribery last July, and officials in key positions had not been properly supervised.

But the inspectors offered rare praise for Chongqing, a city now led by Xi’s protégé Chen Miner. It said the city has “resolutely eliminated the poisonous influence” left by a string of sensational corruption scandals.

The city’s former party chief Bo Xilai, once seen as a contender for the top leadership, and his successor Sun Zhengcai are both serving life sentences for bribery.

Bo’s police chief, Wang Lijun, was also jailed for 15 years in 2012. He triggered one of the most dramatic cases in modern Chinese history when he tried to seek asylum at the US consulate in Chengdu after falling out with Bo, whom he accused of trying to cover up the murder of a British businessman – a crime for which Bo’s wife Gu Kailai was later jailed.

The CDI stressed the need to continue to target “big tigers”, a term used to describe corrupt senior officials, and said “total loyalty” to Xi was essential.

Its report also said officials must perform their duties in accordance with the party’s grand vision and work to improve the environment, one of Xi’s policy priorities.

Observers said that besides targeting corruption, the Communist Party is increasingly using CCDI inspection teams to ensure better performance from officials.

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Alfred Wu, an associate professor at the Lee Kuan Yew School of Public Policy at the National University of Singapore, said inspection teams are now a very important part of the “pressure-centred government model”.

“The strong tone in such [CCDI] reports served as a strong and recurring reminder to officials not to be complacent, especially on the complexity in purging the corrupt elements linked to previous ‘tigers’ and building loyalty to the current party leadership,” Wu said.

“Beijing wants to be 100 per cent sure about stability in these years as it is entering into a tense period of [personnel] reshuffling and deciding on the next leadership team in the 20th Communist Party Congress to be held in 2022.”

Xie Maosong, a political scientist at the University of the Chinese Academy of Sciences, said the inspection groups are increasingly becoming a tool to make sure “people put their heart into their work”.

“Facing a strong anti-corruption campaign, some officials might think it is better to do less to make fewer mistakes,” Xie said. “But the inspectors’ reports now stress not only disciplinary issues, but also their work quality … Inspected units are not only expected to be clean but to show they have put their hearts and minds into their work and been proactive in achieving their targets.”