Every single one of our consumer choices can either have a positive or negative impact - not just on the environment but also on other people's lives too and your banking choices are no exception. You might unwittingly support the arms trade or companies that destroy the Amazon rainforest - now you might protest that the minimal amount of money you have in your bank won't be big enough to influence anything but I disagree: It's not just that every pound you spend on a good cause is one pound less contributing to pollution, environmental degradation, mis-information, human rights abuse or even war. It also shows big business that we don't accept their reckless behaviour anymore and that we are open for alternatives.
Unfortunately most of us will never know what the big banks are really doing and who they are lending money to, if the bonuses have really been earned that they give their employees or if they drive us head-on into the next big financial crash. But there are a few ethical banks and building socieies that are trying to make a positive difference and are a worthy alternative to the big banks on the market:
Triodos - states that it lends "exclusively to organisations who put people and the planet before profits, our savers' money works to create a positive impact and real returns." To make good on their claim, they publish details of every organisation they lend to on their website.
Ecology Building Society - it states that they are "supporting sustainable development across the UK" and it has been rated "Best Buy" for their mortgages and savings accounts by the Ethical Consumer magazine in its product guide rankings (July/August 2016 issue).
Most building societies fare much better than banks, with 5 other BS (Coventry BS, Cumberland BS, Leeds BC, Newcastle BS, and West Bromwich BS) scoring a good 13.5 points out of 20 in the Ethical Consumer magazine.
Abundance Investment - offers ISA accounts and investment options that "create something good for the environment and society, and a good financial return too", as they claim on their website. You can invest in certain projects like housing or green energy projects.
If you have some more cash than you need and you are looking for some ethical and clever ways of investing it, you can find more information on this topic as well here at the Ethical Consumer magazine.