Britain's Co-operative Group has announced the resignation of chief executive Euan Sutherland, throwing the troubled mutual into a fresh crisis.
He will be temporarily replaced by chief financial officer, Richard Pennycook, until a new CEO can be found, the Co-operative said in a statement.
Mr Sutherland has decided to step down after less than a year at the helm, blaming the failure to reform the governance of the mutual that is owned by its 4.7 million customers.
"It is with great sadness that I have resigned," Mr Sutherland said in the official statement.
"I have given my all to the business and had hoped to be able to lead its revival.
"However, I now feel that until the group adopts professional and commercial governance it will be impossible to implement what my team and I believe are the necessary changes and reforms to renew the group and give it a relevant and sustainable future."
The resignation was also sparked by a leak of details of Mr Sutherland's £3.5m pay package for
In a message on Facebook over the weekend, Mr Sutherland blamed "an individual, or individuals" at the top of the group for seeking to undermine him.
The resignation also comes after a tug of war between Mr Sutherland and the group's board of directors over how the supermarkets-to-funeral homes conglomerate should be run.
Mr Sutherland will meanwhile forego a 1.5-million bonus and long-term incentive payments that were due for his role in securing the group's banking division.
The Co-operative Bank came close to collapse last year after the lender was ordered by regulators to increase its capital cushion by £1.5 billion.
The bank - which prides itself on ethical investments - was subsequently forced into a drastic restructuring that handed control to US hedge funds in order to plug the vast black hole.
Co-op Bank slumped into further crisis last November after its former chairman Paul Flowers, a Methodist minister, was filmed allegedly planning to buy illegal drugs.
The bank now faces a series of investigations into what went wrong, and ongoing questions over the appointment and suitability of Flowers, who lacked knowledge of the financial sector.