Four of its non-executives have resigned, bringing to nine the number of directors or senior executives to disappear following the discovery of the financial crisis five months ago.
The latest departures include Len Wardle, group chairman, who is described as a "former university fellow" and a director of Communicate Mutuality, and Duncan Bowdler, a buying manager for the Co-operative Group, as well as external non-executives Bob Newton and Peter Harvey.
In May chief executive Barry Tootell "chose to step down" when the £1.5bn black hole was revealed, three months after the departure of finance director James Mack. Mr Tootell oversaw the failed Project Verde deal to buy more than 600 branches from Lloyds Banking Group.
In June, Martyn Wates and David Davies stepped down from the board, and it emerged that chief IT officer Jim Slack had already left.
The four departing non-executives will be replaced by three independent directors and a new representative of the Co-operative Group, while two existing group representatives - group chief executive Euan Sutherland and Midcounties Cooperative chief executive Ben Reid - will remain on the bank board.
The bank said: "The changes are part of preparation to increase the independence of the bank ahead of the launch of the exchange offer, part of the wider capital action plan announced on June 17."
Hedge funds have succeeded in getting the bank to revisit its original rescue plan, which would force bondholders to contribute £500m or one-third of the total by taking losses.
They include 15,000 investors in the Co-operative's permanent interest-bearing shares (Pibs) and preference shares. Some £370m of Pibs were issued by the Co-operative and the former Britannia building society before its takeover, including £60m held by 7000 small investors mainly pensioners, who would have their coupons paying between 5.5% and 13% a year cancelled.
They would be offered new bonds cutting the value of their holdings by more than half.
However Mark Taber, fixed income expert who has led the small bondholders' campaign, said earlier this week he was concerned the "plan B" plotted by hedge funds was a takeover of the bank, to "carve up the cake and the retail investors will pick up the crumbs".
The Co-operative Bank, which has 4.7 million customers and employs 10,000, plans to list on the stock exchange. Its parent will retain a majority stake after a £1bn capital injection in the rescue. It reported a £709m loss in the first half of this year.
The balance sheet hole stems largely from commercial property liabilities at the Britannia, according to evidence submitted last month to the Treasury Committee.
Andrew Bailey, chief executive of the Prudential Regulation Authority, told MPs that more than 75% of the Co-operative's non-core loan losses in 2012 and around 85%-90% of non-core loan losses in the first six months of this year related to Britannia assets.
The former Britannia and Co-operative Bank chief executive Neville Richardson, who quit the bank in July 2012 receiving some £4m in compensation payments, had told MPs the proportion of impairments was around one third.
Mr Taber wants the bank to fund professional representation for bondholders.