The ratings agency downgraded all three banks to A from A+ citing greater regulation and uncertain market conditions.
In a statement, S&P said the ratings action was due to "increasing risks that Europe's large banking groups active in investment banking face as regulators and uncertain market conditions continue to make operating in the industry more difficult."
(Read More: Portugal Throws New Curve Ball in Euro Debt Crisis )
The ratings agency also affirmed the A/A-1 long- and short-term ratings on Swiss bank UBS.
S&P's outlooks on all these banks are stable.
"It's really difficult to run a global bank right now," said Jim Antos, a bank analyst at Mizuho Securities Asia.
"They are criticized because the regulations are too tough on them and if we didn't have the tougher rules, the ratings agencies would still downgrade the big banks because they would be viewed as not being prudently run," he told CNBC Asia's "Cash Flow" on Wednesday. "This is a no win situation."
Banks globally are facing tighter regulations and the U.S. Federal Reserve said on Tuesday that U.S. banks should expect a range of new rules on top of the Basel III requirements on capital.
(Read More: Fed Approves Key Capital Rules for Banks )
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