Zeng Feiyang, director of the Guangdong Panyu Migrant Workers Center, talks on his phone during an interview in Guangzhou, Guangdong province, January 20, 2015. REUTERS/Alexandra Harney

By Alexandra Harney

GUANGZHOU (Reuters) - As China's economic growth slows, fuelling industrial unrest, independent labour advocates say they have never faced so much intimidation - and they expect it to get worse this year.

In coastal areas like Guangdong province in southern China, the slowdown and rising costs are forcing some factories to close or move inland, often without properly compensating workers.

The number of strikes more than doubled in 2014 to 1,378 from 656 the year before, according to China Labour Bulletin, a Hong Kong-based advocacy group. April saw the biggest strike in decades, when about 40,000 employees of Adidas and Nike supplier Yue Yuen went on strike to demand social insurance payments.

All of which is making work for labour activists such as Zeng Feiyang and Zhang Zhiru, while social media platforms such as WeChat, QQ and Sina Weibo are making it easier for word of industrial action to spread.

It is also increasing activists' run-ins with the police and others in a country where officials see strikes as a threat to social stability, and investors often see workers' rights as a threat to their wallets.

After nearly two decades as one of China’s most prominent labour activists, Zeng, based in provincial capital Guangzhou, is no stranger to trouble. But last month was the first time he had been held overnight in a police station without charge, and twice he has spent the night under police guard at hotels since September.

Zhang, based in Shenzhen, says he has lost count of how many times police questioned him last year.

And he has been forced to move 13 times over the same period because, he says, police told his landlords he was a politically problematic tenant.

Other labour activists tell similar tales.

"The crackdown last year was the toughest in history," says Chen Huihai, director of worker training at leading labour dispute law firm Laowei. "2015 is going to be even tougher."

Police in Guangzhou and Shenzhen did not respond to requests for comment.

On top of the police action, Zeng and Zhang describe other worrying incidents they suspect are related to their labour advocacy.

One morning last month four men came to Zeng's office, accusing him of unpaid debts. Two of them kicked and punched him, breaking his glasses and leaving him with bruises on his leg and back.

Last fall, Zhang's car was doused in gasoline and its rear window smashed.

Both reported the incidents to police, but they remain unsolved and unexplained. Zhang says police did not investigate. The police did not respond to requests for comment.

SQUEEZE ON FOREIGN FUNDING

Activists say the police appear particularly concerned about groups receiving money from outside China.

“The police come to see us regularly. Their main objection is to our foreign funding,” said an employee of advocacy group Beijing On Action International Cultural Centre who asked not to be named. As a result of such pressure, the organisation has stopped most of its work on labour rights.

Zhang's group, Chunfeng Labor Dispute Service Center, has also had to stop taking foreign money, and since October Zeng has not taken funding from China Labour Bulletin under pressure from the police.

Zeng said he had borrowed money from a friend to tide his organisation over until it can find new sources of support.

As officials have stepped up pressure on NGOs, they have been encouraging workers to turn instead to the state-sponsored All-China Federation of Trade Unions (ACFTU), the only legal union in China, which has mostly sat on the sidelines of industrial relations until now.

Under a law that came into effect in Guangdong this month, the chief negotiator for workers in collective bargaining should be the head of the union.

Li Ying, director of the Shenzhen ACFTU's legal department, says the union is "always trying to maximise benefits for workers", but Labour activists doubt that a Communist Party organ that has often sided with management or government can win the trust of people in dispute with their employers.

In which case, workers will still turn to people like Zeng for help.

Though he worries about the consequences of his work for his 10-year-old son and his wife, Zeng says he is undeterred.

"If they put me in prison, I will have no regrets."

(Additional reporting by Shanghai newsroom; Editing by Will Waterman)