Sir John Vickers, the former chairman of the Independent Commission on Banking (ICB), has said banks could be "forced" to separate their retail operations from riskier areas.
Giving evidence to the specially convened Parliamentary Commission on Banking Standards on 12 November 2012, he said domestic retail customers should be "ring-fenced" from other operations.
He added that although he was not in favour of a full break up of banks, such a threat should be kept "in reserve" to ensure that his proposals work.
"If the industry turned out to be unreformable...then it's possible that total separation would turn out in due course to be the better step to take," he said.
But he insisted that was not likely, saying that he expected the ring-fence structure to work.
The parliamentary commission was set up in the wake of the Libor scandal, and is looking at lessons to be learned about corporate governance, transparency and conflicts of interest, and their implications for regulation and government policy.
The Libor scandal emerged in June 2012, when UK and US authorities fined Barclays £290m for fixing a key inter-bank interest rate.
The ICB was set up in June 2010 to consider reform of the banking sector.