More than one-fourth of U.S. households do not use traditional banking services, according to a study released by federal bank regulators on Wednesday.

The Federal Deposit Insurance Corp, the agency charged with protecting U.S. bank deposits, said 25.6 percent of households are "unbanked" or "underbanked."

It said those households are largely either low-income or minority, or both.

FDIC Chairman Sheila Bair said insured bank accounts provide financial security and access to credit on affordable terms.

"By better understanding the households that make up this group — who they are and their reasons for being unbanked or underbanked — we will be better positioned to help them take that first step," she said in a statement.

Bair has championed financial literacy and education, even writing two children's books on the subject: "Rock, Brock and the Savings Shock" in 2006 and "Isabel's Car Wash" in 2008.

The study was conducted by the U.S. Bureau of the Census and found that about 21.7 percent of black households and 19.3 percent of Hispanic households are unbanked, while only 3.3 percent of white households and 3.5 percent of Asian households are unbanked.

Households were characterized as unbanked if no one in the household had a checking or savings account. They were characterized as underbanked if they had a checking or savings account but relied on alternative financial services, such as non-bank money orders, non-bank check-cashing services, payday loans, or pawn shops.

Households with income under $30,000 account for at least 71 percent of unbanked households, the study found.

Results of the study broken down regionally can be viewed at www.economicinclusion.gov.