A report by the Changing Markets Foundation claimed that factories in Asia supplying some of the UK's biggest brands were linked to "devastating air and water pollution".
More than 128,000 people have signed a petition calling on H&M and Zara "and other fashion giants" to stop sourcing from producers linked to pollution, after a report claimed factories linked to the brands were damaging local waterways and emitting "noxious gases".
The Changing Markets Foundation launched the petition last week after publishing a report that claimed to have found evidence of pollution surrounding major viscose fabric manufacturing sites in China, Indonesia, and India.
H&M was found to be buying from eight polluting factories and Zara was buying from four, the report said, though the foundation acknowledged that both businesses had been "among the most transparent" in dealing with the inquiries with regards to their suppliers.
Viscose is a manmade clothing material similar to silk in appearance, but cheaper. It is bought by major fashion brands and is made from wood pulp that is treated with chemicals. The report, published earlier this month, claimed that pollutants from viscose production had seeped into local waterways and air, killing aquatic life and making water undrinkable in some instances.
While the petition specifically targets H&M and Zara, the report also named Tesco, Asos, and M&S among businesses thought to be supplied by factories in those regions.