HONG KONG – Japanese clothing giant Uniqlo has failed to improve abusive working conditions or stop environmental pollution in its supplier factories in mainland China, despite having acknowledged the problems months ago, labor rights groups in the country said Thursday.

Four clothing factories manufacturing goods for the fashion chain were alleged to have abused workers by enforcing overtime work beyond legal limits, using toxic chemicals that harm the workers and pollute the environment and failing to pay for workers’ social insurance and housing fund premiums, according to Sophie Chen, project officer for Students and Scholars Against Corporate Misbehavior (SACOM).

In a report jointly conducted by SACOM and three other labor-related groups and issued in January, the factories were also alleged to have collected fines from workers who failed to meet certain job requirements and ignoring workplace safety.

“In the (Corporate Social Responsibility) report issued by Uniqlo on July 31, the company admitted to some of the issues, made changes such as lowering the shop floor temperature by bettering ventilation and installing troughs to direct the sewage water, (but) the condition of illegal overtime work remained rampant,” Chen, who along with some 20 protesters who stormed the shop’s headquarters in Hong Kong to protest, told the press.

In one case, workers were forced to work without holidays from mid-March to mid-May, accumulating 176 hours of overtime, far exceeding the legal limit of 36 hours, Chen said.

She added that Guangzhou’s environment protection unit has confirmed that a toxic and carcinogenic chemical was found in sewage water released by one of the factories.

The factory has been blacklisted by the authorities, Chen said, and Uniqlo has promised to install equipment to meet pollution standards, but they are not sure of the progress.

The group also alleged that one factory had fired a worker representative after having police detain her for months for leading a protest in June.

“Some 400 local thugs were ordered by the factory to halt the workers’ protest,” another group member said. “Workers were threatened to end the protest and go back to work while the representative was detained.”

Uniqlo said in an email it is studying SACOM’s second report and that some clarification is needed.

“Respecting human rights and ensuring appropriate working conditions for the employees of Fast Retailing’s production partners is a top priority,” said Beryl Tung, spokesman for Uniqlo’s parent company, Fast Retailing Co. “Since this January, Fast Retailing has been enhancing its monitoring and advancing working conditions at the garment factories managed by its production partners.”

In the CSR report, the company said it has increased monitoring of its textile suppliers, cut overtime working hours, and improved the working environment and management style since February.

As of February, there were 325 Uniqlo stores in the Chinese region.

The group had 2,449 stores globally as of August last year.

Tadashi Yanai, the group owner, was ranked this year by Forbes magazine as the richest tycoon in Japan, with a net worth of $21.8 billion.