With child labor present in more than 90% of South India's spinning mills which produce yarn for Western brands, researchers called for the mapping of supply chains and tougher audits.

India is known as one of the world's largest textile and garment manufacturer. The southern state of Tamil Nadu is the country's largest producer of cotton yarn. It is home to some 1,600 mills, employing between 200,000 and 400,000 workers.

The industry has drawn on cheap labor from villages across the state to turn cotton into yarn, fabric and clothes for Western high street shops.

The India Committee of the Netherlands (ICN), a human rights organization, addressed the workers from almost half the mills in the area. The participants for the research were mostly female workers employed in the 734 mills. They were aged between 14 and 18. Up to 20% of the workers were younger than 14.

Most of the workers are young women from poor, illiterate and low caste communities. They are often faced with intimidation, sexually offensive remarks and harassment.

According to the study, employees were forced by their employers to work long hours. The employers were also said to often withhold their pay or lock them up in company-controlled hostels after working hours. Some employees involved in the research also complained being sexually harassed.

Among the hundreds of mills in the area, only 39 mills paid the minimum wage. In addition, in half the mills, a standard working week involved 60 hours or more of work.

The organization also quoted an 18-year-old former worker as claiming that the girls were tortured by supervisors, forcing them to extract work beyond their capacity.

Another teenage girl told the researchers that she was forced to work 12 hours straight, with no breaks for lunch or to even use the bathroom. The abusive working condition caused her to suffer from burning eyes, rashes, fever, aching legs and stomach problems.

"We have raised the issue for five years now, but even to us the scale of this problem came as a shock," ICN Director Gerard Oonk said in a statement.

However, K. Venkatachalam, chief advisor of the Tamil Nadu Spinning Mills Association, said that he was not aware of the research. He even told the Thomson Reuters Foundation that the matter has been closed since the state government had recently filed a report to the Madras High Court stating that such issues were no longer prevalent in the country.

The researchers further cited poor enforcement of labor laws and "superficial audits" by the buying brands. The organization called on the industry and government to map supply chains and publish sourcing details. It has also called for the awarding of rewards to factories that upheld the standards.