Marcel Ospel, criticised for overseeing UBS's first ever annual loss of SwFr4.4 billion (£2.06 billion), has been nominated by the bank for re-election as its chairman at its annual meeting on April 23.

But under proposed new rules each director will now have to be re-elected each year instead of every three years. Mr Ospel said it was his idea to have the new, more limited tenure for board members.

Switzerland's largest bank also appointed the Fiat chief executive Sergio Marchionne, who is already a board member, as non-executive vice chairman. There has been speculation that Mr Marchionne could replace Mr Ospel as chairman.

UBS has been the worst hit of Europe's banks in the credit crisis, sustaining $18 billion (£9.23 billion) worth of writedowns in the collapse of the US sub-prime mortgage market.

Existing board members Larry Weinbach, the former executive chairman of Unisys, and Peter Voser, the chief financial officer of Royal Dutch Shell, will also stand for re-election. Mr Voser will take over from Mr Weinbach as chairman of the bank's audit committee, after Mr Weinbach asked to be relieved of this duty.

Mr Ospel said today that the new appointments, plus the move to put board members up for re-election every year rather than every three years, would "strengthen the leadership structure in order to manage UBS's current challenges".

The bank already has an executive vice chairman, Stephan Haeringer, a long-time UBS employee.

UBS will ask the general meeting to change the bank's articles of association to approve the new terms, so that by 2010 at the latest the entire board will be re-elected on a yearly basis.

Next week the bank will hold an extraordinary meeting for shareholders to approve a capital injection of SwFr13 billion from GIC, the sovereign wealth fund of the Singapore Government, and an unnamed Middle Eastern investor, in return for a 9 per cent stake in the bank.

The cash will be used to strengthen UBS's tier 1 capital.

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