Supermodel Helena Christensen models M&S womenswear

Ms Yusuf, who joined M&S from rival Warehouse, will step down from her role as creative director of womenswear at the end of September to go it alone.

Her departure is seen as a blow for an M&S trying to rebuild sales after seeing off a recent hostile takeover from clothing tycoon Philip Green.

Once the nation's favourite, M&S recently lost its crown as the UK's largest clothing retailer to Asda.

Ms Yusuf joined M&S three and a half years ago, and her first clothing range for the company, called Limited Collection, met with critical acclaim and consumer enthusiasm.

More changes

"Yasmin has made a significant contribution to womenswear," said M&S chief executive Stuart Rose.

"She has improved our design capability, developed our approach to 'top to toe' dressing, and played an important part in launching Limited Collection."

Ms Yusuf's departure comes as Kate Bostock, product director of Asda's George clothing range, is set to join M&S as director of womenswear.

Ms Bostock, who arrives in October, will replace Steve Longdon, who was sacked back in the spring after disappointing sales.

"Yasmin has put in place a system that will ensure continuity in design," said an M&S spokeswoman.

"We believe we have got a really good team who can take things forward."

By 1400GMT on Thursday M&S shares were down 1.2% to 350.5p.