Fashion retailer H&M Hennes & Mauritz is responding to concerns that Uzbek cotton is getting into its supply chain by forcing suppliers to sign up to new commitments and encouraging one of its suppliers to buy out a stake owned by Korean conglomerate Daewoo.

H&M has strengthened its supplier requirements to prevent Uzbek cotton knowingly getting into its supply chain. It will now ask suppliers and critical fabric mills to sign a commitment that their cotton does not come from Uzbekistan. Those who do not sign the commitment will not be allowed to work with H&M.

The announcement follows accusations from Anti Slavery International in December, which claimed that despite pledging not to source Uzbek cotton, H&M refused to take steps to guarantee no companies in its supply chain "profit from slavery in Uzbekistan".

According to the human rights group, around 90% of Uzbek cotton is harvested by hand, with half of all cotton picked by state-sponsored forced labour, and children as young as nine forced to work for up to three months a year to fill the shortfall in voluntary adult labour.

The country is the sixth largest producer of cotton in the world, and the third largest exporter, earning over US$1bn through the export of around 850,000 tonnes of cotton each year.

According to the charity, Korean conglomerate Daewoo International runs three large cotton processing facilities in Uzbekistan. Daewoo processes cotton from all over the world, and sells cotton yarn and clothing to apparel companies, which means it is difficult to know which products come from Uzbekistan.

While H&M has pledged not to buy cotton from Uzbekistan, the Cotton Campaign told the retailer that Daewoo was a small part owner of a supplier to H&M. The supplier has now bought out Daewoo's remaining share and is now the company's full owner.

The deadline for signing the commitment is 28 February.