Moody’s has downgraded the credit ratings of Bank of America and Wells Fargo over concern that government support would be unlikely should they become financially troubled.

The ratings of Bank of America Corporation’s (BAC) holding company were lowered to Baa1 from A2 for long-term senior debt and to Prime-2 from Prime-1 for short-term debt. The long-term deposit ratings of Bank of America (BANA) were downgraded to A2 from Aa3, while BANA’s short-term rating was affirmed at Prime-1. The actions conclude a review for downgrade announced on June 2, 2011. The outlook on the long-term senior ratings remains negative.

The long-term ratings of Wells Fargo’s holding company senior debt were lowered to A2 from A1 and of its major subsidiaries including Wells Fargo Bank (rating on the bank for deposits were lowered to Aa3 from Aa2). The actions conclude a review for downgrade announced on June 2, 2011. The outlook on the long-term senior ratings remains negative.

According to Moody’s, “the downgrades result from a decrease in the probability that the U.S. government would support the bank, if needed. Moody’s believes that the government is likely to continue to provide some level of support to systemically important financial institutions. However, it is also more likely now than during the financial crisis to allow a large bank to fail should it become financially troubled, as the risks of contagion become less acute.”

Moody’s said it is lowering the amount of support it incorporates into Bank of America and Wells Fargo’s ratings to levels reflected prior to the crisis.

To read the full Moody’s ratings action on Bank of America click here.

To read the full Moody’s ratings action on Wells Fargo click here.