The Co-operative Bank will poll nearly five million personal and business customers today as it updates its ethical policy following a bail-out by investors last year.
The bank nearly collapsed after a £1.5 billion hole was found in its balance sheet and the wider Co-op group now has a stake of just 20% in the business, which previously owned it outright.
But the bank's chief executive Niall Booker said its ethics continue to be central to its identity.
He said: "The Co-op is not like other banks. Our heritage, ethos and values are different.
"That is why it is so important to renew and refresh our values and ethics to ensure that the next chapter of the bank is true to its heritage and translated to today's world."