And in a blinding glimpse of the obvious, the Fed also urged banks that “communications with consumers should provide clear and balanced information about the relative benefits and risks of the products.”

Even these tepid suggestions raised the banks’ ire: Their representatives called the guidance an example of regulatory overreach.

So it’s not surprising that the more aggressive stance taken by the C.F.P.B. has enraged big financial institutions and their supporters in Washington. Just last month, for example, it sued Navient, the giant student loan servicer, charging it with cheating borrowers, allegations the company denied. And in early February, the bureau sued a New Jersey-based legal funding company, alleging that it swindled first responders to the World Trade Center attack out of money they were owed from victim compensation funds.

One of the C.F.P.B.’s best features is its unusual complaint process, in which it acts as intermediary between consumers who believe they have been wronged and the companies they have had problems with.

Consumers can call the bureau’s complaint hotline or file a grievance online. They can also check the database to see if others have experienced the same problem with a company. The bureau says its call centers — one in Iowa and another in New Mexico — field roughly 25,000 calls each month; its website receives about 22,000 complaints monthly.

Since July 2011, the bureau has handled over one million such complaints, sending them to the companies and ensuring that they respond. It has published more than 700,000 of these grievances on its website.

“Complaints can really tell us about business practices that pose risks to consumers,” said Darian Dorsey, deputy assistant director for the office of consumer response at the bureau, in an interview. “We take all this information together to understand the problems consumers are experiencing and to enable the bureau to improve the marketplace.”