UBS has reported a new asset writedown of $19bn, more than doubling its total writedowns as a result of the sub-prime crisis to about $37bn (£18.5bn).
It has already written off $18.4bn in 2007.
The bank says it is planning on raising 15bn swiss francs in capital by issuing new shares.
UBS has also confirmed that its chairman and former chief executive Marcel Ospel will not be seeking re-appointment.
The announcement came as the bank says it expects to post a first quarter net loss of $12.1bn.