Len Wardle, who recently resigned from his post on the board of Co-op Bank, will give up his chairmanship in May next year after serving in the role since 2007.
Mr Wardle is one of the final senior managers to depart after being involved during Co-operative's disastrous takeover of Britannia Building Society and its unsuccessful pursuit of 632 Lloyds Banking Group branches under the Project Verde banner.
The Co-op, which traces its roots back to 1844 with the Rochdale Pioneers, is finalising a rescue plan for its banking arm, which will avoid a taxpayer bailout but cede control to owners of its bonds including US hedge funds Aurelius Capital Management and Silver Point Capital -prompting fears of a customer exodus.
Separately, Peter Marks, former Group chief executive, told the Treasury Select Committee yesterday that the fact the Co-operative would end up with just 30% of the equity in its bank as part of that deal to plug a £1.5 billion capital hole was a "tragedy" but may end up being a good thing for the Group.
He said: "In actual fact it will focus Co-op to focus on less businesses and not stretch its capital in the way it has done."
Mr Marks said he had warned the Group it should focus on fewer businesses but the corporate structure meant he did not have the power to change the strategy during his six years in charge.
Mr Marks stuck doggedly to the position that he did not have individual responsibility for the bank and said: "I could not be accountable as I was not approved by the [Financial Services Authority] to run a bank. That was not my role in the organisation. I can't take responsibility for something I am not in full control of."
Mr Marks, who retired from Co-operative in August, sat on the bank board as a non-executive director and admitted he was one of the main drivers of the Verde deal to acquire 632 branches from Lloyds Banking Group.
Neville Richardson, former Co-op Bank chief executive, previously told the Committee he left his role as he felt the transaction would have been "absolutely disastrous".
Mr Marks said the Verde deal, which Co-operative Group looked at for two years before abandoning it in April this year, would have brought capital, IT infrastructure and a strong management team.
He said: "I was not acting alone. This was not Peter Marks plc. This was a joint effort from the bank team and the retail team.
"The bank, in our view, was sub-scale and needed to build scale and survive. Verde was a great opportunity to build that scale and bring significant capital."
When pressed by the Committee for his reaction to concerns raised in December 2012 by Lloyds Banking Group about Co-operative Group's ability to do the deal, Mr Marks admitted he could not recall the details.
He said: "There were lots of conversations and I can't remember every one."
Asked whether Verde had been a catastrophic misjudgment, Mr Marks replied: "No. Our examination of this opportunity is not at the heart of what happened to the bank. This acquisition would have brought capital into the bank."
Mr Marks indicated the transaction to buy Britannia, which later proved to have large volumes of impaired loans, was driven by Mr Richardson, then at Britannia, and the then Co-op Bank chief executive David Anderson.
However, Mr Marks admitted he had voted for the deal and said: "Of course I share responsibility. Should we have bought Britannia? If we had had a crystal ball, of course we wouldn't. "
Asked if the Britannia deal could be categorised as a "disastrous error", Mr Marks said: "I think disastrous error is harsh but it certainly was an error."