"The conclusion was very surprising to me, in terms of the way that the bank was resolved through this very unusual sale to UBS, with associated unusual payments to shareholders versus bondholders," Winters told an audience at the Qatar Economic Forum, organised by Bloomberg.

Winters also said a banking crisis was over but that a transformation of banks was still needed.

Qatar Investment Authority CEO Mansoor Ebrahim al-Mahmoud told the same audience he thought UBS had got a "good deal" with the Credit Suisse takeover.

UBS has flagged tens of billions of dollars of potential costs - and benefits - from its takeover of Credit Suisse, underscoring the high stakes involved as it prepares to complete the rescue of its struggling Swiss rival.

Under the rescue deal, engineered by Swiss authorities over one March weekend amid global banking turmoil, UBS agreed to buy Credit Suisse for 3 billion Swiss francs ($3.4 billion) in stock and to assume up to 5 billion francs in losses that would stem from winding down part of the business.

The first rescue of a global bank since the 2008 financial crisis, which is backed by up to 250 billion Swiss francs in public funds, will create a wealth manager with more than $5 trillion in invested assets and over 120,000 employees globally.

(Reporting by Andrew Mills; writing by Lisa Barrington; editing by Jason Neely and Sharon Singleton)