Standard & Poor’s on Tuesday cut its credit ratings for many of the world’s largest banks, including Citigroup (NYSE: C), Goldman Sachs (NYSE: GS) and Bank of America (NYSE: BAC).

The move follows S&P’s shift, announced earlier this month, in the methods it uses for rating the banks.

Citigroup, Goldman Sachs and Bank of America Corp. each had their long-term credit rating downgraded a single notch to A- from A. Similar cuts were applied to JPMorgan Chase (NYSE: JPM), Wells Fargo & Co. (NYSE: WFC) and Morgan Stanley (NYSE: MS).

Dozens of other banks were also affected by S&P’s new criteria and many of the downgrades stemmed from the affected banks’ exposure to the European debt crisis. S&P cited weaker confidence in governments’ ability to bail out struggling banks.

The new criteria for rating banks comes in the wake of criticism leveled at all three major rating firms – Moody’s and Fitch’s are the other two — that they rubber stamped their highest ratings on investment products loaded with subprime mortgages in the years leading up to the financial crisis.

Congress has considered reforming ratings system to remove perceived conflicts of interest.

S&P alerted the markets and the banks of the pending changes in March 2010 and again in January 2011. Analysts praised the ratings firms for their communication with affected banks as the new criteria was being established.

British banks that also saw downgrades include Barclays, HSBC Holdings, Lloyds Banking Group and The Royal Bank of Scotland.

However, due to the complexity of the new criteria, ratings for several big European banks, including Credit Suisse, Deutsche Bank, ING and Societe Generale remained unchanged despite the ongoing debt crisis there.