Marie Melnyk has resigned as managing director of Morrisons after taking medical advice.

She will leave on 22 December after more than 30 years at the supermarket chain and will then consider her options for the future. The company declined to elaborate on her decision.

Melnyk has been one of the leading female figures in the grocery industry for many years and had been one of the favourites for the chief executive post eventually filled earlier this year by Marc Bolland.

She joined Morrisons in 1975 and became produce director in 1987. A year later, she was made trading director and was closely involved in setting up Morrisons' central grocery facility in Wakefield.

In 1993, she was appointed to the main board of directors and took on responsibility for buying and marketing. In 1997 she became deputy managing director and in March 2002 moved up to the role of joint managing director. Two years later she became sole managing director.

"I have been privileged to have been with the company and to work within the British food industry for the past 30 years," said Melnyk. "This is the right decision for me and is at an appropriate time, given the company's improving position under the leadership of our new chief executive."

Bolland will temporarily take on Melnyk's board responsibilities. "In the short time I have worked with Marie, I have been impressed by her skills and experience and I am particularly grateful for the time she has spent supporting my own induction into the business. She leaves with my best wishes for the future," he said.

Morrisons chairman Sir Ken Morrison said: "Marie has made an immense and immeasurable contribution to the company's success.

"We are sad to see her go and thank her for all that she has done."