Consumers now make one-third of their in-store purchases with a debit card, according to the American Bankers Association, an industry trade group.

But as many users have discovered, the debit card carries the same problem as its credit card cousin – you can spend over your limit, causing yourself financial havoc.

The practice of approving a check or debit transaction when the account has insufficient funds is an intentional effort to drive up revenues, according to a new study by the Center for Responsible Lending.

“Banks should protect customers’ funds, not plunder them with high fees and harmful practices,” said Eric Halperin, director of CRL’s Washington office.

Many banks and credit unions automatically enroll customers for overdraft protection programs when they open a checking account, according to CRL. When an overdraft occurs, the financial institution will advance the funds but charge a fee. For the privilege of a short-term loan to cover the shortfall, the customer is charged on average $34, according to CRL’s data.

In hopes of reducing overdraft fees charged to consumers, the CRL is supporting legislation (H.R. 946) that would, among other things, require banks and credit unions to warn their customers before authorizing an electronic overdraft.

Bankers argue that overdraft protection is not only something consumers want but also need, considering many do overdraw their checking accounts.

“It helps to avoid embarrassment, inconvenience, merchant fees and other adverse consequences of having a check bounce or a transaction denied,” Nessa Feddis, senior federal counsel for the ABA, said in recent testimony before a House subcommittee.

Feddis said it’s the responsibility of the customers to keep track of their money.

Still, why won’t the institutions warn customers about possible overdrafts?

“Current technology makes real-time notification of overdrafts cost prohibitive,” Feddis said.

Interpreted another way: Financial institutions don’t want to change the status quo because they make good and easy money off their own customers’ mistakes or irresponsibility.

The fact is, Halperin said, that the technology exists and should be installed to deny a transaction if there isn’t enough money in a person’s account.

On this issue, everyone should be held accountable. Consumers have many ways to check what they have in their accounts before using their debit cards. To cover themselves when mistakes happen, they can link their checking account to a source of backup funds – a savings account or line of credit. Or they could just opt-out of having overdraft protection.

And financial institutions should restrain their fee frenzy and stop routinely allowing consumers to withdraw funds that exceed their account levels, only to slam them with overdraft charges.