Sir Philip Green, billionaire owner of the Arcadia retail group that includes Topshop, said in a statement Shepherdson had resigned after deciding it was "time for a change".

He denied Shepherdson, who is credited with turning the fast-fashion house into a brand worn by stars and trendy teenagers alike, was leaving because of a deal signed last month to have Moss design a Topshop range.

"For clarification, Sir Philip and Jane would like to confirm their unanimous agreement to sign a design collaboration with Kate Moss for Topshop, and this has absolutely nothing to do with her decision to leave the business," Green said in a statement.

Topshop announced its design deal with Moss, for an undisclosed sum, to a fanfare of publicity last month, with Green saying he aimed to turn clothes created by the supermodel into a global brand.

Fashion press welcomed it as success for Moss, giving her a new platform to a new career outside modelling, and for Shepherdson, who turned a cheap high street chain into a fashion brand by rapidly replicating catwalk styles at discount prices.

Britain's The Times reported on Thursday Shepherdson was in last-ditch talks with Green after complaining that she was not consulted properly over the hiring of Moss.

Green, denying the report, told Reuters he and Shepherdson had been discussing her departure for a number of weeks. He said he was not aware of her future plans. Two Topshop veterans will be taking over her role.

Shepherdson, described as the most important woman in UK fashion by industry journal Drapers, was not immediately reachable.

But fashion editors, many in Paris for fashion week there, were already mulling Topshop's future without its star director and if her loss will weaken in its race against fast-fashion rivals like Hennes and Mauritz and Zara.

"Jane did a terrific job at creating the Topshop we know today. She's left it in great shape for the team and whoever new comes in to take it on to another phase," British Vogue Editor Alexandra Shulman said from Paris.

Topshop is the crown jewel in Green's Arcadia group, which he bought for ?¡ê800 million in 2002. He has had plans to expand the group to the United States next year, although he told Reuters on Thursday nothing was yet on the drawing board.