Issuing a warning to national banks, Comptroller of the  Currency Eugene A. Ludwig on Thursday said the quality of affordable   mortgage portfolios has deteriorated.   
"We have recently noticed some decline in asset quality and increased  delinquency patterns in some national banks' affordable mortgage   portfolios," Mr. Ludwig told the National Association of Affordable Housing   Lenders in Dallas.     
  
"These patterns, while not pervasive, underscore the importance of  effective credit underwriting standards and portfolio credit risk   management processes," he added.   
Many national banks have only recently begun offering affordable  mortgages, which generally require low down payments, Mr. Ludwig said.   Therefore, these institutions are not very experienced in underwriting   these loans.     
  
Within the next month, the agency plans to issue an advisory letter  detailing the credit quality problems. It will recommend how national banks   can better manage their affordable mortgage portfolios.