Lending standards at U.S. banks are increasingly stringent, according to the Federal Reserve's April 2008 Senior Loan Officer Opinion Survey on Bank Lending Practices.

The survey showed tighter lending terms and standards for mortgages, business loans and credit cards between January and April. The Fed said 55% of domestic banks reported higher lending standards for commercial and industrial firms, and 80% reported tighter lending to consumers.

"The net fractions of domestic banks reporting tighter lending standards were close to, or above, historical highs for nearly all loan categories in the survey," said the report.

Lending criteria for real estate rose at 80% of U.S. domestic banks and at more than 55% of foreign banks, while 30% of domestic banks tightened credit card lending standards.

David Ader, U.S. government bond strategist at RBS Greenwich Capital, said cautiousness from lenders is a growing theme "as the near-term prospects for the economy become more and more uncertain".

"Things have yet to reach the early-90s levels for the consumer side, but the trajectory shows a concerning trend for the broader economy," he wrote in a note to clients.

By Adam Button and edited by Stephen Huebl