One of Britain's most popular fashion chains is under pressure to sever its links with clothing suppliers that buy cotton from Uzbekistan, where large quantities are harvested using child labour.

H&M, the giant fashion chain which uses football star David Beckham and singer Lana Del Rey in its advertising campaigns, has signed a pledge to "not knowingly" source cotton from the central Asian country in response to concern from human rights groups. Uzbekistan, one of the world's largest exporters of cotton, forces adults and children as young as nine to pick cotton under what the charity Anti-Slavery International describes as "appalling conditions".

However, it is hard to trace Uzbek cotton back to its source.

Much of it ends up in Bangladesh and China. As a result, many fashion chains canΆt guarantee that their clothing is free of Uzbek cotton.