Over 100,000 people opened accounts with The Co-operative Bank during the summer.
The Co-operative Bank has seen significant growth in customers moving from rivals with the number of people switching up 43% year on year.
It added that at its peak, when there was a succession of issues that beset some of the larger banks, the bank saw a 90% increase in customers requesting to switch.
Robin Taylor, head of banking, at The Co-operative Bank, said: “This data provides further evidence of how The Co-operative Bank is recognised as a genuine and trusted alternative for banking on the high street.
“Feedback from customers that have recently switched has shown that the instigator for them was a desire to have a bank they could trust, underpinned by a responsible approach to banking and an ethical policy that directs who the bank will and will not finance.
“This, combined with a large range of competitive products and award winning customer service makes us a compelling alternative in the market.
“Unlike other banks which are owned by their shareholders, we are member owned.”