Kate Bostock, Marks & Spencer’s clothing supremo, has sensationally stepped down “by mutual consent” with the retailer after clothing sales went into tailspin.

Bostock, Marks & Spencer’s general merchandise executive director, will leave in October. She will be replaced by John Dixon, who has steered Marks & Spencer’s food business to success and has spent 26 years at the retailer.

Former Jaeger and Debenhams chief executive Belinda Earl will also join Marks & Spencer as style director, working two to three days a week and reporting to Dixon. Retail director Steve Rowe will take charge of food.

In its first quarter, M&S’s group sales edged down 0.7%. In the UK, total sales fell 0.9%. While food was up 2.9%, general merchandise was down 5.1%.

UK like-for-likes fell 2.8%. Food nudged up 0.6% but general merchandise plunged 6.8%.

Marks & Spencer chief executive Marc Bolland thanked Bostock for her work at M&S and insisted the decision about her departure was mutual. He said: “We are both agreed that this is the right time for her to be moving on from Marks & Spencer.”

He said that Dixon is the right person to take responsibility for general merchandise. Bolland said: “John has done an outstanding job in running the food division over the past four years.He will be working closely in his new role with Belinda. She is a highly experienced retailer and her product knowledge and judgement will complement John’s expertise. We are delighted that she has chosen to join us in this new role.”

Although Earl will only work at M&S three days a week, Bolland said that is “a long time” to spend specifically on clothing rather than general merchandise overall. Her impact is expected to be seen in the spring/summer collection next year.

M&S said of first-quarter trading: “Clothing sales continued to be impacted by the merchandising issues in our spring/summer collections reported in April, but we have taken steps to strengthen the team, improve our buying and merchandising, and bring stock back on target for the Autumn/winter season, which launches in stores later this month.

“The clothing market continued to be highly promotional throughout the quarter, especially in womenswear, in part due to unseasonal weather conditions. This affected categories such as casual tops, which, given our high market share, are key performance drivers at this time of year.”