At some banks in 2011, more than 40 percent of all new customers opted in to overdrafts, while other banks had only single digit opt-in rates, the CFPB reported.
In March, Rep. Carolyn Maloney, D-N.Y., introduced the Overdraft Protection Act of 2013, which directs the CFPB to limit overdrafts to one per month or six per year, and prohibits banks from manipulating the order of transactions to maximize overdraft fees.
Maloney's legislation would require that overdraft fees "be reasonable and proportional," and codify the Federal Reserve opt-in provisions.
Wu said financial institutions make what she calls "misleading statements" when asking if customers want to opt in. She said banks need to make it clearer what opting in means.
"They made it seem that consumers would be worse off if they did not opt in, whereas we think they are better off not opting in," Wu said.
Wu urges consumers to confirm with their financial institutions that they have opted out of overdrafts.
"Consumers who did not opt in get charged a lot fewer overdraft fees and save a lot of money. Go to your bank and say, 'I don't want debit or ATM overdrafts. There's no harm in telling your bank you're opting out."