Marks & Spencer's (M&S) clothing chief has resigned just weeks ahead of a crucial Christmas trading period that the City believes will shape the tenure of Steve Rowe, the company's boss.
Sky News has learnt that Jo Jenkins, who has held the role of director of clothing and beauty, for just a few months, is to leave to join White Stuff, a privately owned clothing chain.
Her defection will be seen as a bitter blow to Mr Rowe, who took over as M&S's chief executive last year.
He recruited Jill McDonald, who ran the bicycles retailer Halfords, as managing director for clothing, home and beauty in May, but her lack of fashion retailing experience has been questioned by City analysts.
Ms Jenkins was seen as a crucial part of M&S's clothing executive team, but is said to have been disappointed to have been passed over for the role that was handed to Ms McDonald.
A source close to M&S said that Ms Jenkins' departure was expected to be announced shortly and was likely to be brought forward as a result of the leak to Sky News.
Mr Rowe faces a crucial test of his credentials during the next three months, with Archie Norman, the retail veteran who has just taken over as M&S's chairman, understood to be closely scrutinising every area of the company's operations.
While M&S's food operations have continued to perform well – despite a slowdown disclosed in July – Mr Rowe needs to demonstrate that he can inject sustained growth back into its clothing operations.
Last year, he announced a plan to shut some underperforming stores and reallocate space in others.
M&S could not be reached for comment.