Shares of the largest banks in United States tumbled on Wall Street after Calyon analyst Mike Mayo downgraded the stocks with an underperform rating.

We are initiating on U.S. banks with an Underweight sector rating given the ongoing consequences of increased risk taking by banks in seven different areas, Mayo said.

Citigroup shares decline 13 cents to 4.56% at $2.72., While, Bank of America down 12 cents to 1.58% at $7.48 and Wells Fargo shares $1.09 to 6.67% at $15.25.

Government intervention might not help as much as expected, especially given that loans have been marked down to only 98 cents on the dollar, on average, he said, and expects loan losses at the banks to be as bad as the Great Depression by 2010.

In addition that The U.S. government has $7.6 Trillion Left to Fix Banks, according to the reports and has tapped $3.1 trillion to date in efforts to resolve the current financial crisis, roughly 29% of the $10.7 trillion it has at its disposal, according to research published Monday by Keefe, Bruyette & Woods.

Expect loan losses to increase from 2% to 3.5% given the ongoing problems in banking such as mortgage, consumer credit, gluttony of real estate and industrial, sloth-like risk management, pride of low capital, envy of exotic fees, and anger of regulators, Mayo said.