UBS AG, already wincing from massive write-downs caused by the subprime crisis, has taken another blow as a former CEO is pushing the Swiss bank to separate its private client operations from the stumbling investment unit.

A shareholder group cheered the proposal from the bank's former CEO, Luqman Arnold, and investors agreed, sending its stock higher on Friday.

UBS has reported write-downs of US$37.4 billion (euro23.65 billion) for the past nine months - so far the largest reported by any bank with exposure to US defaults on risky mortgages. It expects first-quarter losses of 12 billion Swiss francs (US$12.1 billion; euro7.65 billion) and that it would seek 15 billion francs (US$15.1 billion; euro9.55 billion) in new capital.

Arnold, who was dismissed as CEO in 2001 in what was seen as a power struggle, said that may not be enough.

"We are not convinced that the 'one bank' integrated business model that has served UBS well in the past will survive the damage inflicted by the proprietary trading losses and write-downs," Arnold said in a letter dated Thursday from his investment firm Olivant Ltd.

UBS spokeswoman Tatjana Domke confirmed that the bank had received the letter and said it would respond in due course.

Below are the loss leaders in the subprime debacle: