This is no ordinary drop in sales, this is ... M&S

Kate Bostock, who is responsible for clothing ranges as head of general merchandise, will leave the group in October, with former Debenhams and Jaeger boss Belinda Earl coming in as style director.

Ms Earl is credited with transforming Jaeger’s “dowdy” image and rolling out the highly successful “Designers At Debenhams” range.

Investors hope she will do the same at M&S after critics said the retailer no longer appeals to the under-35s, who have switched to more fashionable brands such as Zara and online fashion store ASOS.

The group’s problems have been firmly blamed on non-food, where underlying sales fell by 6.8 per cent in the three months to June 30 – the worst performance since December 2008.

Food sales put in a credible performance with a 0.6 per cent uplift, boosted by the Diamond Jubilee in June.

M&S is now worth less than arch rival Next on the London stock market, while ASOS added to the strain on M&S by reporting a better-than-expected eight per cent rise in UK sales yesterday.

Some analysts said Ms Bostock has been made a scapegoat for chief executive Marc Bolland as he fights for his job.

The pair are said to have had a tense relationship.

But there have long been rumours of Ms Bostock’s departure, and she has been linked with ASOS.