While most mainstream banks argue that their behaviour is ethical, there are several banks that make a point of emphasising their ethical credentials. This usually involves ruling out investments in certain sectors, such as arms, or refusing accounts to companies regarded as immoral.
Each bank of this sort has its supporters who argue that it is ethical and its critics who insist that it is not ethical enough. It is worth looking at the ethics and practicalities of each bank to reach your own decision.
You may find it helpful to look at the “Switching Scorecard” published by Move Your Money, which rates the ethics of each bank and building society in the UK.
Here’s a summary of UK-based banks that make a point of promoting themselves as ethical.