"Same work, unequal wages" is one of the banners that workers at the VW factory in the northeastern Chinese province of Jilin waved in a recent video posted to YouTube.

Around 1,500 temporary staff are demanding up to 200,000 euros per person in lost wages at the Changchun plant, which the German carmaker operates with its Chinese counterpart FAW.

According to the Hong Kong-based rights group China Labor Bulletin, a promise of arbitration in their case, mid-February, has been delayed. According to Chinese law, employment mediators must decide within five days whether to accept a case.

Full hours, half pay

With the deadline elapsed, workers want to bring their case to court. They claim that the VW-FAW joint venture has been using temporary workers for a decade or more, but has only paid them half of what permanent staff can earn.

The workers are not only demanding lost wages, but also compensation for other unpaid allowances, claiming that the agency that hired them, Changchun Hongxin Youye Human Resources, has violated China's labor law.

Volkswagen has three major joint ventures with Chinese firms, allowing it to become the second-largest foreign car maker

"The right to equal pay has been one of the key elements in the revision of the Chinese labor code in 2012 to tackle the widespread grievances (among temporary staff)," said Cynthia Estlund, a law professor at New York University and an expert on Chinese labor law.

Estlund, who is the author of the book "A New Deal for China's Workers?" told DW it's not unusual for Chinese workers turn to arbitration bodies first before going to court. She said there's no reliable data available on number of worker complaints since the revised labor code came into force. However, Chinese sources suggest there are as many as ten thousand disputes per year.

Keeping workers content

China's state and party leaders have long been worried about the potential for growing worker unrest. Rather than see the rise of an independent workers' movement, Beijing has put its faith in arbitration services, to help mediate solutions to staff grievances.

But some employers think the revised labor law has gone too far in strengthening workers' rights, in an attempt by Chinese leaders to prevent social unrest. Many companies argue that China's economy is not yet developed enough for such high labor standards. Estlund told DW there are calls for the law to be further revised to offer greater "flexibility" for employers.

Hamburg-based lawyer Rolf Geffken revealed that workers had not only cited Chinese labor law in their case, but also Volkswagen's temporary work charter, which was agreed with VW Group's "World Works Council" in November 2012.

In a YouTube clip, temporary VW-FAW auto workers complain their rice bowl is tiny in comparison to full time staff

"In fact, refusal to pay the same salary is both against Chinese law and (VW's) Temporary Work Charter," said Geffken, who has more than a decade's experience working with the Chinese labor law.

The Chinese code defines temporary work as positions that "do not exist for more than six months." It explicitly states that temporary staff are entitled to the same pay for the same work as full time staff, Geffken told DW.

"According to these terms, the employment of most of those affected temporary workers in Changchun is illegal. The workers have a right to permanent employment and the same salary," he added.

State media silent

Reports of workers' protests are mostly never reported by China's fiercely state-controlled media. All too often, any criticism uploaded to social networks will quickly disappear too. But protesters can sometimes get round the country's famous online censors, nicknamed "The Great Firewall of China."

VW-FAW's temporary workers managed to post videos to YouTube, where they demanded the companies "Pay back what we worked for with our blood and sweat."

Unless the companies honor Chinese labor law, they declared, "the only way forward is to go to Beijing."