Human rights activists have called on Nike to stop doing business with Daewoo International, which they claim is the largest processor of forced labour cotton in Uzbekistan.

A letter sent to the sporting goods firm highlights how the government of Uzbekistan has forced millions of children, teachers, public servants and private sector employees to pick cotton under appalling conditions.

"Those who refused are are expelled from school, fired from their jobs, denied public benefits or worse," it said.

"The government combines these penalties with threats, detains and tortures activists seeking to monitor the situation and continues to refuse the International Labor Organization's efforts to monitor the cotton harvest," the letter said.

The letter claims that Nike, which promised to stop buying Uzbek cotton in January, is knowingly doing business with a company that is profiting from slave-picked cotton.

However, Nike only sources synthetic material from Daewoo International, the International Labor Rights Forum said.

Daewoo International has been blacklisted by a number of other leading apparel brands, including H&M, The Limited, C&A, and Eileen Fisher.

"Nike would apparently rather harbor companies in its supply chain that are profiting from human rights violations than help bring an end to Uzbekistan's heinous forced labour system," said Umida Niyazova, founder of the Uzbek-German Forum for Human Rights.

Earlier this year, H&M encouraged one of its suppliers to buy out the stake in its company owned by Daewoo International, after H&M was accused of breaking its commitment not to source cotton from Uzbek.

Responding to the claims, a Nike spokesperson told just-style: "We continue to reiterate our commitment not to incorporate cotton from Uzbekistan into our products. We have taken internal steps to require that our contract manufacturers do not use materials containing Uzbek cotton for Nike and our affiliate production. Those steps include surveying our apparel vendor base on cotton sources using our Apparel Materials Cotton Spinning Location Report managed by the Global Apparel Materials Manufacturing team."