Switzerland's largest bank UBS failed to address nagging concerns about further possible write-downs yesterday, dishing out instead a restructuring of top management and sending shares to a fresh 10-year low.

UBS, Europe's biggest casualty of the credit crisis so far, and under fire from investors for shoddy corporate governance, said it would dismantle the office of chairman, a key demand of one of its top shareholders investment group Olivant.

"There is talk that UBS will propose another capital hike," a Zurich-based trader said. UBS is under pressure from the Swiss financial watchdog and investors to overhaul its business after more than $37 billion (Dh135.8bn) in write-downs during the global credit turmoil. "Apparently, UBS blames its corporate governance – with a chairman who also had executive power and no real supervisory function – for its sub-prime debacle," said Landsbanki Kepler analyst Dirk Becker.

"With its new governance, it wants to ensure that such an accident can never happen again. However, as this won't help to get it out of the current crisis, we regard this announcement as a nonevent," Becker said.

Recommendations of a governance committee – including strengthening the board's oversight role and a clear separation of the responsibilities of the board of directors and executive management – would be implemented immediately, UBS said. Olivant had criticised the chairman's office for having too much sway over executive management.

Four board members would resign and replacements would be elected at an extraordinary general meeting planned for October 2, UBS said.

Sergio Marchionne, chief executive of Italian automaker Fiat SpA, would fill a new post as senior independent director, and continue as non-executive vice-chairman of UBS.

The board and its strategy committee are continuing their review of the strategic positioning of the bank and its businesses, UBS said.