UBS AG shareholders Wednesday refused to absolve the board and management who ran the bank in 2007 for that year's substantial losses, raising the possibility of civil charges.
A slim majority of nearly 53% of shareholders voted against the so-called discharge, an unprecedented move and a sharp rebuke from increasingly vocal investors.
Chairman Kaspar Villiger said the vote was a "clear sign of dissatisfaction" that the board of the Zurich bank would take very seriously.
In 2007, UBS suffered $18 billion in losses on illiquid housing securities, leading to a 4.38 billion Swiss franc annual loss ($4.14 billion) that year.
The vote marks the first time in Swiss corporate history that a board proposal has been rejected by shareholders, many reports said Wednesday.
