A controversial ban on petitioning for unpaid back wages by groups of migrant workers was announced Saturday by Shenzhen government for the five months ahead of the August 12 Universiade Games.

"Those who organize or participate in such a petition will be held accountable in accordance with relevant regulations," the announcement read on the official website of the city's housing and construction bureau.

"If their actions cause serious consequences, they will face criminal charges," the statement said.

A southeastern metropolis on the border with Hong Kong, Shenzhen is known for its floating population of migrant workers who fill factories and construction sites.

It has 12 million floating residents out of a total population of nearly 14.5 million, according to 2010 data.

The new rule was plain unfair, said Wang Yanbing, a welder from northwestern Shaanxi Province who has worked and lived in Shenzhen more than 10 years.

"To seek payment of arrears by going solo will always guarantee you get completely ignored," he said. "If you're lucky, you might hear something from the local labor authorities after a long time. We really don't have too much choice."

Migrant workers "made a contribution to the Universiade Games," a worker told the China National Radio on Sunday on condition of anonymity. "Now the city government tells us that we will be punished for petitioning to defend our rights. This is not fair at all."

Payment arrears remain a long-term issue that threatens China's social stability.

Vowing first to tackle those construction companies that refused to pay arrears, the bureau warned migrant workers against turning up in groups at city petition bureaus.

Group petitions can disrupt social order and so it was "reasonable for local government to issue such a regulation for an international event," said Hong Daode, a criminal law professor at the China University of Political Science and Law in Beijing.

The new rule has "no legal basis," Zhou Ze, a lawyer at Beijing Wentian Law Firm, told the Global Times.

"Petitioning is entitled by the Constitution as the right of every Chinese citizen and no government department has the power to ban petitioning," Zhou said. "The local authorities have no legal authorization to implement such a provision.

"They should have tightened regulation of construction companies that fall within their powers."

The bureau is a governmental organ, Zhou said, not a law enforcement body.