NEW YORK — For years, Wells Fargo employees secretly issued credit cards without a customer’s consent. They created fake email accounts to sign up customers for online banking services. They set up sham accounts that customers learned about only after they started accumulating fees.

On Thursday, these illegal banking practices cost Wells Fargo $185 million in fines, including a $100 million penalty from the Consumer Financial Protection Bureau, the largest such penalty the agency has issued.

Federal banking regulators said the practices, which date back to 2011, reflected serious flaws in the internal culture and oversight at Wells Fargo, one of the nation’s largest banks. The bank has fired at least 5,300 employees who were involved.

In all, Wells Fargo employees opened roughly 1.5 million bank accounts and applied for 565,000 credit cards that may not have been authorized by customers, the regulators said in a news conference. The bank has 40 million retail customers.

Some customers noticed the deception when they were charged unexpected fees, received credit or debit cards in the mail that they did not request, or started hearing from debt collectors about accounts they did not recognize. But most of the sham accounts went unnoticed, as employees would routinely close them shortly after opening them. Wells Fargo has agreed to refund about $2.6 million in fees that may have been inappropriately charged.

Wells Fargo is famous for its culture of cross-selling products to customers — routinely asking, say, a checking account holder if he or she would like to take out a credit card. Regulators said the bank’s employees had been motivated to open the unauthorized accounts by compensation policies that rewarded them for opening new accounts; many current and former Wells Fargo employees told regulators they had felt extreme pressure to open as many accounts as possible.

“Unchecked incentives can lead to serious consumer harm, and that is what happened here,” said Richard Cordray, director of the Consumer Financial Protection Bureau.

We l l s Fa r go s a i d t h e employees who were terminated included managers and other workers.

“Wells Fargo is committed to putting our customers’ interests first 100 percent of the time, and we regret and take responsibility for any instances where customers may have received a product that they did not request,” the bank said in a statement.

Many of the questionable accounts were created by moving a small amount of money from the customer’s current account to open the new one.

Shortly after opening the sham account, the bank employee closed it down and moved the money back, according to regulators.

But Wells Fargo employees were still most likely able to get credit for opening new accounts in meeting their sales goals, the regulators said.

On Thursday, the bank stressed that the refunds have been relatively small — averaging about $25.