Cases of salary cuts or pay defaults involving migrant workers increased by 34 percent in the first three quarters, partly due to the ongoing economic downturn, according to a trade union official.

Zhang Bo, an official at the All-China Federation of Trade Unions, said such cases and other violations of workers' rights are still rampant, especially in Guangdong, Anhui and Heilongjiang provinces and the Inner Mongolia autonomous region.

"They are no longer limited to the construction industry - they have spread to the manufacturing sector as well," he added.

According to the business news website Yicai.com, only 30 percent of manufacturing companies can pay wages on time. Many such companies are facing financial strains and are having to make huge layoffs.

Last year, there were 274 million migrant workers in China, with an average monthly income of 2,864 yuan ($572.8), according to a National Bureau of Statistics report released in April 2014.

The report said 0.8 percent of the migrant workers, or 2.19 million, could not receive their pay on time.

The average salary amount in default was 9,511 yuan. More than 60 percent of the migrant workers did not sign labor contracts with employers.

Zhou Litai, a lawyer specializing in protection of migrant workers' rights and interests, said the situation this year could be even worse because the economic downturn has affected many traditional industries.

"The wage cuts and defaults happened mostly in the construction sector. Most migrant workers cannot get their money until a project is completed," said Zhou, who is based in Chongqing.

"Many projects were illegally outsourced several times before they were officially started.

"What is worse, some project contractors borrowed money from loan sharks. When they receive payment for the project, they have to pay the loan sharks first, and then have no money for the migrant workers," Zhou said.

Zhang said his federation would support the government in establishing a monitoring and warning system on salary-related issues to help migrant workers get paid. "Some local trade unions also explored a new mechanism to ensure migrant workers receive payment. For example, the union in Shanxi province has set up a fund that will pay migrant workers first before getting the money back from their employers."

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