More U.S. consumers have fallen behind on loan payments than ever before, and the problem may worsen as millions more find themselves out of a job, a study released today (April 2) shows.

According to the American Bankers Association (ABA), which represents most large U.S. banks and credit card companies, the percentage of consumer loans at least 30 days late rose to a seasonally adjusted 3.22% in the October-to-December period from 2.29% in the prior quarter, according to Reuters.

The ABA said the fourth-quarter rate was the highest since it began tracking the data in 1974, with delinquencies rising in nearly every category. It said these credit trends are unlikely to improve before 2010.

“Job losses have really hurt the economy and will continue to inflict pain for several months,” James Chessen, the ABA’s chief economist, said in an interview. “The greater the losses are, the more severe an impact it has on all credit markets.”

The ABA study covers direct auto, indirect auto, closed-end home equity, home improvement, marine, mobile home, personal and recreational vehicle loans. It excludes bank credit card and education loans.

“We’ve seen delinquency rates across the board in consumer loans go up, and continue to go up,” Bank of America Corp. CEO Kenneth Lewis said today on CNBC television. But he said “early” delinquencies, or payments missed shortly after loans are taken out, have begun to abate in a “smattering” of products at the largest U.S. bank.

According to the ABA, the late-payment rate on auto loans made through dealers rose to a record 3.53% in the fourth quarter from the third quarter’s 3.25%, while late payments on home equity lines of credit rose to a record 1.46% from 1.15%.

RV loan delinquency rates rose from 1.27% to 1.38% but remained the lowest among all the categories measured.

A report issued Wednesday by ADP Employer Services said U.S. private employers shed a record 742,000 jobs in March, pushing year-to-date losses above 2 million.

Economists polled by Reuters expect the Labor Department to say on Friday that the U.S. jobless rate rose to 8.5% in March, a level not seen since 1983, from February’s 8.1%.