A Citigroup spokesman said the lender required “annual training for our foreclosure employees on the proper execution of affidavits, including having personal knowledge of the information in the affidavit.”

A Wells Fargo spokeswoman said “the affidavits we sign are accurate.” A spokesman for Bank of America, Rick Simon, said, “We do not have anything to tell you at this time.”

GMAC and Chase are in trouble because, overwhelmed with foreclosures, they tried to process them as quickly and cheaply as possible, defense lawyers say. The companies say they are reviewing their procedures to take care of any violations.

The missteps stemmed from the affidavits the lenders file as they seek a quick or summary judgment in thousands of foreclosure cases. The affidavits state certain facts about the case, including the amount owed, which the signer indicates he has personal knowledge of. Without the affidavit, the lender would have to prove the facts at trial.

In depositions taken by lawyers for homeowners, executives at GMAC and Chase said they or their teams signed 10,000 or more affidavits and related documents a month. That did not give them time to review the cases.

Defense lawyers say the disclosures are symptomatic of the carelessness, if not outright fraud, that lenders have been exhibiting for years in their rush to file cases. Many necessary documents have disappeared, with defense lawyers saying the lenders often do not even have standing to foreclose.

In a number of pending cases in Florida, defense lawyers there said, GMAC has already withdrawn affidavits. The lawyers said they would try to have the cases thrown out for possible fraud, although they acknowledged that might be difficult.