Iman has called for a boycott against racist fashion labels.

The 58-year-old supermodel is urging people to take a stand and bombard designers who refuse to use black models in their catwalk shows with messages via social media.

She said: ''It feels to me like the times need a real hard line drawn like in the 60s, by saying if you don't use black models, then we boycott.

''If you engage the social media, trust me, it will hurt them in their pockets. If you take it out there, they will feel the uproar.''

The model-turned-businesswoman - who is married to David Bowie - believes the fashion industry is going backwards and is horrified by the racism displayed in castings.

She told The New York Times: ''There is something terribly wrong. We have a President and a First Lady who are black.

''You would think things have changed, and then you realise that they have not. In fact, things have gone backwards.''

According to the newspaper's figures, only six per cent of catwalk models at New York Fashion Week in February were black, falling from 8.2 per cent in 2012.