Standard & Poor's on Tuesday downgraded 24 Italian banks and financial institutions, citing renewed "market tensions" and lower economic growth prospects.

The action was taken after a review of the implications of a tougher-than-previously-anticipated macroeconomic and financial environment for the Italian banks, the credit rating agency said.

"In our opinion, renewed market tensions in the euro zone's periphery, particularly in Italy, and dimming growth prospects have led to further deterioration in the operating environment for Italian banks," it said in a statement.