The Liberal Democrat manifesto includes measures to ensure banks can't charge customers unfairly for going over their limit or bouncing a cheque.
Other policies include a cap on interest rates charged by credit cards and store cards, and real terms cuts in rail fares.
Commenting, Nick Clegg said:
"A Liberal Democrat government will legislate to ensure that no bank can charge its customers unfairly for going over their limit or bouncing a cheque.
"Banks should, of course, be able to pass on the costs they incur in dealing with these problems.
"But they should not be able to profiteer from customers making small mistakes. We will outlaw unfair charges from now on.
"Bank bosses should look to their consciences and give back the money they took from their customers in unfair charges.
"It can't be right that someone who buys just a few items can end up being charged hundreds of pounds in unfair fees.
"I believe bank bosses have a moral obligation to pay that money back. If they had a shred of moral decency, they would never have imposed these charges and they would never have refused to pay them back.
"Together Barclays, Lloyds, HSBC and RBS have given out more than £7bn in bonuses in the last year alone.
"How can they refuse to return a few hundred pounds they wrongly took from people struggling to make ends meet from week to week?"