The chairman of the Co-operative Group resigned this morning following a Mail on Sunday drugs sting operation.
Len Wardle announced his departure with immediate effect after the Group’s former bank chairman Paul Flowers was embroiled in a drugs scandal.
Wardle led the board who decided upon Flowers’ appointment.
The Methodist minister was filmed buying drugs including cocaine and crystal meth from a dealer in Leeds.
Flowers was appointed to the £132,000 a year job as chairman of the ethical Co-operative Bank in 2010. He stepped down in May after the bank almost collapsed.
Methodist minister Flowers has also been suspended from the Labour Party while drug taking allegations are investigated. It has since emerged that he was forced to resign as a councillor in Bradford in 2011 after "inappropriate but not illegal adult content" was discovered on a computer he was using.
Wardle said: "The recent revelations about the behaviour of Paul Flowers, the former chair of the Co-operative Bank, have raised a number of serious questions for both the bank and the group.
"I led the board that appointed Paul Flowers to lead the bank board and under those circumstances I feel that it is right that I step down now, ahead of my planned retirement in May next year.
"I have already made it clear that I believe the time is right for real change in our operations and our governance and the board recently started a detailed review of our democracy.
"I hope that the group now takes the chance to put in place a new democratic structure so we can modernise in the interests of all our members."
The supermarkets-to-funerals group last night launched a fact-finding probe about into "any inappropriate behaviour" and a "root-and-branch" review of its structure in the wake of the revelations about Flowers.
Critics have questioned how he could have been appointed given his apparent lack of experience, and Andrew Tyrie, chairman of the Treasury Select Committee, said that, even before the weekend's revelations, it was clear he was "manifestly unsuitable".
The Co-operative Bank is facing a rescue plan which will see majority control turned over to investors including US hedge funds, after it was left with a £1.5 billion gap in its finances following the takeover of the Britannia Building Society in 2009.
Flowers, a former Bradford councillor, now faces a police investigation. He has apologised over the scandal and been suspended by the Methodist Church as well as the Labour Party.
Wardle's departure will see him replaced by his deputy, Ursula Lidbetter, chief executive of the Lincolnshire Co-operative.
The Co-operative Group said: "It is intended that Ursula will chair the group through the current governance review, which will include consideration of how the board is constituted and chaired."