The three had had all worked at the Panyu Workers’ Centre in the southern province of Guangdong and had been in detention since last December.

Among the trio is the centre’s manager, Zeng Feiyang, who was handed a four-year suspended sentence, a close friend told The Telegraph on Tuesday.

Zeng’s mother, Chen Wenyin, had previously told The Telegraph about her anguish after state media reported “slurs” that her son had defrauded workers and used prostitutes, in what she described as “trial by media”.

His colleagues at the centre, Tang Huanxing and Zhu Xiaomei, were each given 18-month suspended sentences at a court hearing Monday, the friend said.

The activists were said by state media to have been charged with “disturbing social order”, a phrase often used by China’s stability-obsessed authorities to clampdown on dissent.

Images of the court proceedings shown on state television showed Zeng admitting to receiving funding and training from “overseas organisations hostile to China”.

Chinese media has previously been accused of showing ‘forced confessions’ of opponents of Beijing.

The three activities had helped many workers achieve better pay and conditions, their supporters say.

Authorities had previously tolerated such calls from Chinese workers when the economy was booming.

But the recent slowdown has seen a shift in manufacturing to other parts of Asia where lower wages are paid – such as Vietnam – and this has become a concern for Beijing.

The closure of factories is more common in China’s southern manufacturing heartland.

Xi Jinping, the Chinese President, has promised to strengthen the rule of law, and Beijing says that it is acting to ensure the fair treatment of suspects.

However, human rights groups said President Xi is overseeing a wide-ranging crackdown on civil society which has seen lawyers, activists and government critics being targeted.

Independent trade unions are banned in China, which recognises only the All-China Federation of Trade Unions as a means of solving disputes.