The clothing and food group said on Monday Laura Wade-Gery, executive director, multi-channel, will not return following her period of maternity leave and will officially leave the company on Sept. 30 after five years at the firm.

In December Wade-Gery had extended her leave until Sept. 1.

However, in April Steve Rowe succeeded Marc Bolland as chief executive. A month later he shook up the responsibilities of his executive team and simplified the firm's management structure, sparking speculation on whether there would be any role for Wade-Gery.

In the past the former Tesco executive had been tipped by some as a possible successor to Bolland, though her star waned somewhat in 2014 when M&S's new online platform got off to a shaky start.

"I've been away from the business for a year now, and that time has seen some significant changes in both my personal life and in the business," she said in a statement. "I concluded that the time was right to move on from M&S."

Wade-Gery's agreed departure will see her receive monthly payments of up to a maximum of eight months' salary and benefits, subject to mitigation.

Rowe, a 26-year M&S veteran, has pledged to turn around M&S's struggling clothing business by improving ranges and availability, cutting prices and offering fewer promotions.

However, his plan, outlined in May, came with a warning of a short-term dent to sales and profit and in July the 132-year-old group reported its worst quarterly clothing sales for a decade.

Shares in M&S, down a third over the last year, closed down 5 percent at 326 pence.

(Reporting by James Davey; editing by Susan Thomas)