Paul Tucker, the deputy governor for financial stability, has admitted no obvious answer exists to what he deemed the biggest problem to be underlined by the financial crisis.

Speaking at the annual conference of the International Institute of Finance, a global banking trade body, in Istanbul on Sunday, Tucker said having banks that were too big to fail was untenable and put the problem at the crux of the exit strategy from the financial crisis.

"We need to exit from the regime of the past