The nation’s largest banks have tightened their lending standards in all major loan categories in the past three months while both household and business demand have weakened, according to the Federal Reserve’s latest Senior Loan Officer Opinion Survey.

The Fed says 65 percent of the big domestic banks surveyed had tightened their lending standards on C&I loans to small firms over the past three months, up from 50 percent in the April survey. The portion that reported tightening lending standards on C&I loans to large and middle-market firms rose slightly over the same period to about 60 percent.

“Very large majorities of domestic and foreign respondents pointed to a less favorable or more uncertain economic outlook, their bank’s reduced tolerance for risk, and the worsening of industry-specific problems as reasons for tightening their lending standards and terms on C&I loans over the past three months,” the report noted.

The July survey also noted a further weakening of C&I loan demand, particularly from smaller firms. “Substantial majorities of domestic institutions that experienced weaker loan demand over the past three months cited a decrease in customers’ needs to finance investment in plant or equipment as well as firms’ decreased need to finance inventories,” the Fed reported.

Eighty percent of the banks surveyed said they had tightened commercial real estate lending standards in the last three months, about the same portion as in the April survey.

Large majorities of domestic bank respondents reported having tightened their lending standards on prime, nontraditional and subprime mortgages over the past three months and 75 percent said they had tightened underwriting standards on prime mortgages — up from 60 percent in the April survey.

The survey also revealed that 30 percent of the domestic banks had securitized or sold conforming-jumbo mortgage loans to Fannie Mae or Freddie Mac over the past three months.