Stella McCartney. [Photo/Agencies]

Stella McCartney has donated a signed sketch to a charity art auction.

The fashion designer has given her drawing to the sale, which will benefit children with special needs and the auction will also feature works by David Hockney, Damien Hirst, Gavin Turk and 22 other contemporary artists.

Although Stella is not an official patron of the Special Yoga Centre - which specialises in providing yoga therapy and other support for children with cerebral palsy, down's syndrome and epilepsy - she helps out in other ways, and has supplied the children attending the centre with clothes for the past several years.

Jo Manuel, founder and director of the charity, said: "The art auction is the main fundraising event of the year and this year is extra special. The centre's move to West Hampstead will provide us with a ground-floor space accessible to wheelchair users, and providing facilities that children and families are in dire need of."

Honorary patrons of the charity include British Prime Minister David Cameron's wife Samantha Cameron and Trudie Styler.

The Special Yoga Centre's 6th Annual Art Auction will be held at the Twentieth Century Theatre in Notting Hill on Tuesday May 15, 2012, from 6 until 10pm.