Swiss financial giant UBS says it will make a first-quarter net loss of $12.1bn as a result of the recent credit market turmoil.

Writedowns on investments hit by the crisis in the US sub-prime mortgage market have more than doubled to a whopping $37bn (£18.5bn).

The firm announced $19bn of fresh asset writedowns on top of the $18.4bn it wrote off last year.

The US sub-prime problems have hit the profits of banks worldwide, as rising mortgage defaults and falling US property prices have meant loans bought by banks are worth less than thought.

Zurich-based UBS also confirmed that its chairman Marcel Ospel would not seek re-election.

Peter Kurer, currently general counsel of UBS, is expected to succeed Mr Ospel as the new chairman.

Looking ahead, UBS said 2008 would be a challenging year for the company.

UBS will publish full first-quarter results on May 6.