In recent days the party has sent out a questionnaire to officials across the country asking them to identify the number and details of "unnatural deaths", including suicides, of party members since December 2012.

The crackdown has so far led to warnings or disciplinary action for about a quarter of a million cadres but it has also been accompanied by a sharp rise in suicides among officials, according to numerous Chinese media reports.

The Chinese Communist party has launched a nationwide survey to ascertain how many of its members have committed suicide since President Xi Jinping unveiled an anti-corruption campaign two years ago.

That is when President Xi launched the graft clean-up that has become his most prominent policy since he took power in November that year.

As well as hundreds of thousands of "flies", as party rhetoric describes low-level officials, Mr Xi's anti-corruption drive has also netted dozens of high-ranking "tigers", including the former head of China's domestic security services, Zhou Yongkang, and former vice-chairman of the Chinese military, Xu Caihou.

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China's state-controlled media have published several articles vilifying allegedly corrupt officials for killing themselves while under investigation but for family members and associates of these officials suicide is often considered the most honorable course of action.

That is because their death will bring about the end of any investigation into their alleged corruption, protecting any accomplices or associates and allowing their families to keep their assets, ill-gotten or otherwise.

Officials found guilty of corruption are not only handed lengthy prison sentences or even the death penalty; they and their families are invariably stripped of generous state pensions and all their assets.

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Children of disgraced officials are also sometimes forced to leave prestigious schools or high-profile jobs.

China's main anti-corruption body, the Central Commission for Discipline and Inspection, is in effect an extralegal entity with enormous powers to detain indefinitely and "discipline" any of the country's 87 million party members.

Legal scholars, family members and rights activists in China have raised serious concerns about the prevalence of torture in CCDI investigations and several of the "suicides" reported in the past two years are believed to be cover-ups of deaths that happened during torture sessions.

In the latest survey, party officials are asked to fill in forms specifying key details of "unnatural deaths", with extra information required if the death is recognized as suicide.

The form lists causes of death including jumping under a train, jumping from a building, hanging, drowning or wrist-slashing. It also requires information on the "cause of suicide", listing psychological disorders, work pressure, family disputes and involvement in illegal activity.

If a suicide took place during an anti-graft probe, officials are asked to say who the main target of the investigation was.