Moody's has downgraded the ratings of 15 global banks due to their significant exposure to volatility and the risk of outsized losses inherent to capital markets activities.
The sweeping move included a drop of Barclays' credit rating by two notches, while both HSBC and RBS had one notch knocked off their credit rating.
The rating actions concluded a review initiated on 15 February when Moody's announced it would be undertaking a reassessment of the volatility and risks creditors of firms with global capital markets activities face.
"In the past these risks have led many institutions to fail or to require outside support, including several firms affected by today's rating actions," Moody's said in a statement.
It added the actions do not only reflect the credit implications of capital markets operations, but also the size and stability of earnings from non-capital markets, capitalisation and presence of liquidity buffers as well as other considerations such as their exposure to Europe, risk management and exposure to US residential mortgages.
Credit Suisse was the only bank to be downgraded by three notches, while in total 10 firms fell two grades and four dropped one.