Iman says not using enough black models on the catwalk is a ''racist'' act.

The 58-year-old former supermodel - along with Naomi Campbell and Bethann Hardison - recently sent a letter to the governing bodies of each fashion capital which highlights a lack of racial equality in the fashion world and claims it is becoming an increasing problem.

The star - real name Iman Mohamed Abdulmajid - clarified on 'Good Morning America': ''This [the letter] is not the business of shaming. As we go back to clarify this, no one is calling any of these designers racist. The act itself is racist.''

Iman believes there was more ethnic diversity when she first started out in the modelling world than there is now.

She added: ''There were more black models working in the 70s than there are in 2013. This a time where silence is not acceptable at all. If the conversation cannot be had publicly in our industry, then there is something inherently wrong.''

Iman, Naomi and Bethan are currently campaigners for the Diversity Coalition, which seeks to create equality in the modelling industry.