After Xiao Yue lost her job working in a factory in northeastern China – among the thousands who were laid-off by sweeping reforms of State-run enterprises at the turn of the last decade – she travelled to the Chinese capital in search of work.

Like many young rural migrant women who ended up in Beijing, struggling to find work without a high school education, she turned to prostitution.

An industry that had all but disappeared after the People’s Republic was founded in 1949 following the Communist revolution has become widespread in China after three decades of economic “reform and opening up”, employing, according to a United Nations estimate, between four and six million people.

Although ubiquitous in China today, the sex industry has become an increasingly unsafe profession, where sex workers are exposed to almost routine abuse even at the hands of law enforcement authorities, according to a new report published on Tuesday by Human Rights Watch (HRW).

The study, based on interviews with 75 women sex-workers in Beijing, documents their lives and difficulties, detailing the abuse they face at the hands of police and the little recourse they have to justice.

Ms. Xiao, from northeastern Heilongjiang, found herself in police custody four years ago following a raid. She was beaten by police to extract a confession, without which the police would have been unable to detain her. “I was beaten until I turned black and blue, because I wouldn’t admit to prostitution,” she said in an interview. “They attached us to trees, threw freezing cold water on us, and then proceeded to beat us”.

The sex industry in China, although illegal, has become widespread, often functioning with the tacit backing of local police officials, according to HRW.

Publicised crackdown campaigns that the police launch, often to coincide with important political events, have led to “increased incidences of police brutality” as well as “arbitrary arrests and detentions” and “physical violence”, HRW says.

The crackdowns, the report suggests, have become counterproductive, making the industry less safe by “driving the trade further underground” and “effectively increasing the vulnerability of women who engage in sex work to police and client abuse.”

The crackdowns “also induce some sex workers to engage in higher risk sexual behaviour,” the HRW report says. For instance, sex workers said that because of the crackdowns, “they stopped carrying or using condoms for fear that the police would use their possession of condoms as evidence of prostitution” as they had done in many cases.

While officially regarded as one of China’s “six social evils” – the others are gambling, superstition, drug trafficking, pornography and human trafficking – prostitution has become widely prevalent in China, with sex workers often openly employed in karaoke venues, hotels and nightclubs.

The government periodically launches “sweep away” campaigns that last several weeks, during which police raid entertainment venues and detain sex workers. Campaigns in the past have been accompanied by controversial “shame parades”, where suspects are made to walk through city streets. After a media campaign in 2010 hit out at the campaign as infringing on the rights of suspects, the parades have been phased out.

The HRW report calls on the government to stop the practice of “sweeps”, which enables abuses, and to also lift restrictions on civil society organisations in China that work for sex workers’ rights and to promote health awareness. It also recommends the "removal of criminal and administrative sanctions against voluntary, consensual adult sex work and related offenses, such as solicitation".

Jing Ying, a 23-year-old sex worker from Sichuan, said in an interview it was common for police to extort sex workers for their services, particularly during raids, and it was impossible to report any abuses considering that they were considered criminals to begin with. HRW also found that State health agencies, such as the Centre for Disease Control (CDC), were themselves harming – and not helping – sex workers, by carrying out forced HIV tests and also mistreating patients.

“Failure to uphold the rights of the millions of women who voluntarily engage in sex work leaves them subject to discrimination, abuse, exploitation, and undercuts public health policies,” the report says.