The number of new customers at the nation’s credit unions more than doubled last year, due in part to the increasing number of customers looking for a way to avoid bank fees.

Recently, the Consumer Financial Protection Bureau launched a broad investigation of overdraft fees charged by banks and began soliciting public input on a new disclosure box about fees that would be included in monthly statements. Some banks that were considering new fees reversed course after public outcry.

“Big banks need to pick their poison,” said Jeremy T. Rosenblum, a partner in Ballard Spahr’s Consumer Financial Services practice. “They can passively accept government-mandated revenue losses, or they can charge new fees and risk offending consumers and, worse, bureaucrats who have been given enormous power over them.”