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Xiao Yong used to hold up placards at protests, demanding that China's leaders declare their assets in a call for political transparency and accountability. But he stopped after men began following his father around and urging him to persuade his 39-year-old son to drop his activism.

"I started to dread that my father's health would deteriorate because of this," said Xiao, a former employee at a state electrical utility in the southern city of Shaoyang. "The government was working on my family members, talking to them and instilling fear in them."

To deter political and social activists, Chinese authorities routinely target their family members, friends and associates, pressuring them to be unwilling agents of persuasion or penalizing them directly.

The practice is rooted in China's centuries-old tradition of collective punishment, although guilt by association has been officially renounced and is explicitly banned under the country's criminal law.

Yet it remains in the playbook of authorities who want to coerce people into submission by sending police and government employees to talk with relatives of targeted activists. Sometimes they use more menacing tactics, such as blocking children from their schools, stripping spouses of employment and placing relatives under investigation for fraud.

Experts say the practice is on the rise because of increasing pressure to keep social stability, and that it is very effective.

"By making the parents or the children suffer, (the authorities) try to prevent the target person from continuing," said Eva Pils, an international law scholar at King's College London. "And it's very effective because of the guilt you feel for bringing all this anxiety and suffering to them."

Independent Tibetan writer Tsering Woeser, who has defied government censorship to document events in her home region of Tibet, said her mother, siblings and friends have been summoned by authorities and urged to dissuade her from writing. They also have been threatened with unspecified punishments, the writer said.

She said her brother, fearing for his job, has not spoken to her for two years.

"I am in a state of isolation," Tsering Woeser said in an interview from the Tibetan capital of Lhasa. "It is shameless that this government should want to achieve its end by involving my family and friends."

The practice has been acknowledged by China's state media, which even has criticized local government officials in cases where they have used such coercion to get residents to give up land slated for lucrative development.

When a government worker in the southern city of Shaoyang was suspended from work after his mother, uncle and aunt refused to take a government offer to move out of their family land, the Communist Party-run People's Daily lashed out.

"It is not only immoral but also lawless to coerce people into submission through kidnapping family affinity," the paper said. "This has become a malicious tumor by bad governance that triggers public anger."

However, authorities have not spoken out similarly over the stifling of political or social activism.

Xiao, the man who held up placards, was detained a couple times for activism that he started in 2007, but he carried on — until government workers began to shadow his father.

"Ideals are ideals. Reality is reality," Xiao said. "I have aging parents and a young child, and I must be responsible to them."

Calls to the Shaoyang propaganda office were answered by a man who said he had no knowledge of such coercive methods.

The tactic sometimes backfires by hardening opposition among relatives who are incensed by the unfairness and find support through social media.

In the southern city of Guangzhou, Wang Aizhong, co-founder of the loosely-knit Southern Street movement calling for an end to China's one-party rule, said when he was detained earlier this year for disturbing public order, his interrogators warned him that his wife, her brother, and even her uncle would lose their jobs if he did not cease the activism.

But Wang refused to yield, and his wife stood by him.

"Every person who has decided to take up the fight will face pressure," said Wang, now released on parole. "Someone has to push for democracy, and I would bring harm to the movement if I should withdraw." Guangzhou police did not immediately respond to a request for comment.

Wang's wife delivered a scathing open letter to the authorities to pledge her support for her husband and demand his freedom: "Please release your evil hands and let my husband come home!"

During her time in university, 22-year-old Liao Minyue was called in by school officials who criticized her mother's activism, and classmates were warned to keep an eye on her. After she started working at an advertising agency, police showed up, first asking supervisors to monitor her and later announcing an investigation into the business.

"Seeing all the troubles I was bringing in, I resigned," said Liao, who lives in the southeastern city of Xinyu.

When she was younger, Liao tried to convince her mother to stop her activism, but her attitude changed after police detained her mother last year for publicly calling for government authorities reveal their personal assets.

Liao now champions the same causes, and has no regrets even though police have revoked her passport and she faces dim job prospects.

"When I witnessed how the authorities played with the law to arrest my mother, I decided to join her, supporting not only my mother but all that have the courage to defend our rights," she said.