Garment makers supplying H&M, Armani and Gap and others are evading norms laid out by the UN's International Labour Organisation (ILO), thanks to loopholes and poor oversight, Human Rights Watch said.
Factories allegedly discriminate against pregnant workers, mandate overtime, pursue anti-union measures, hire minors, and use short-term contacts to avoid addressing workers' needs, according to the report titled Work Faster or Get Out: Labour Rights Abuses in Cambodia's Garment Industry, released Thursday.
Work spaces can be poorly ventilated and workers often receive insufficient bathroom breaks, it added.
"We are like slaves - not workers," one garment factory worker was quoted as saying in the report.
"These global apparel brands are household names," said Aruna Kashyap, senior women's rights researcher at the New York-based organisation. "They have a lot of leverage, and can and should do more to ensure their contracts with garment factories are not contributing to labour rights abuses."
Poor conditions persist despite oversight by the Ministry of Labour and the ILO programme Better Factories Cambodia set up in 2001. The government was also criticised, for fining a number of factories that remains "abysmally low when compared to the number of factories overall and the persistent patterns of labour rights violations," the report said.
Cambodia's garment industry employs more than 700,000 people, 90 percent women, and is a leading source of exports, the report said. Human Rights Watch surveyed 270 workers in 73 factories across Cambodia. Other international brands called out in the report are Adidas, Joe Fresh and Marks and Spencer.
Adidas said it was working with the ILO to ensure better conditions, fair wages and union representation. It also highlighted improvements to the food supplied to the workers at its suppliers' factories.
"During 2014, 1,299 factory visits (including 1,172 factory audits)were undertaken," Silvia Raccagni, senior manager of sustainability communication, wrote dpa by email. "We focus our efforts in higher risk countries."
Media representatives from the other brands did not reply to requests for comment. Monitoring primary suppliers may fail to detect labour violations by subcontractors, the report said.
"Small factories that subcontract to larger export-oriented factories are more likely to hire workers on a casual basis, making it harder for workers to assert their rights because they risk being easily fired," the report said.