Naomi Campbell said her generation of supermodels never thought about being celebrities but she has now learned to use her fame to help others.
Campbell, who is at the forefront of the Fashion for Relief campaign to help Haiti following the devastating earthquake in January, said Nelson Mandela told her in 1992 that she should use her celebrity status to help others but "at 22 years old I didn't really quite understand what that meant".
The model, who admitted she had been through "ups and downs", seemed an unlikely ally for the Prime Minister's wife, Sarah Brown, but Campbell said she was "honoured" to be asked to support the White Ribbon Alliance for Safe Motherhood which aims to make pregnancy and childbirth safer for women and babies across the world.
The model told BBC News Mrs Brown was "an extremely amazing woman" and she was "blown away" when she heard about the number of women and babies who died every day because of lack of training, medical equipment and medicine.
Fashion for Relief has already raised millions to help Haiti and much of the money will be used to support women and children.
Campbell, who plans to visit Haiti after Easter, said she had "quietly" worked with charities for many years and only supported causes she felt passionate about.
"My whole generation of girls, we never thought about celebrity, didn't enter our vocabulary. We just liked our jobs, liked working, liked travelling the world," she said.
Asked about the pressure on young people to live up to glamorous role models, Campbell said it was now a different era as "reality TV has taken over a lot".
She said she liked shows which taught people skills, like X Factor, but was concerned that other shows simply criticised without giving people anything positive.
She said in careers like modelling people had to learn how to deal with criticism and rejection.
Campbell, who stressed "I'm not perfect" despite her glamorous image, was wearing a Fashion for Relief fundraising T-shirt designed by Vivienne Westwood which features a pair of bare breasts.
Earlier this month Campbell organised a fashion show for the Haiti appeal which featured models and celebrities like Kate Moss, Dame Shirley Bassey, Linda Evangelista and funnymen David Walliams and James Corden on the catwalk.
The designer clothes worn at the show will be sold on http://www.net-a-porter.com from March 15.