The Serious Fraud Office said that it hopes to reveal within a month whether it will bring any criminal prosecutions in relation to the bank rate-rigging scandal on Monday.
Barclays chairman Marcus Agius announced he was stepping down over the affair on Monday morning, which saw the British banking sector drawn into controversy over the fixing of inter-bank lending rates.
Questions were again raised over the practices of banks in the UK as Barclays was fined £290 million by UK and US regulators for manipulating the Libor, the rate at which banks lend to each other last week.
A statement from the SFO said "the issues are complex" and added it is "considering whether it is both appropriate and possible to bring criminal prosecutions".
As the Government revealed plans to launch an internal inquiry, which will begin with Barclays chiefs appearing before the Treasury Select Committee this week, Deputy Prime Minister Nick Clegg increased pressure on banking bosses, incuding embattled chief executive Bob Diamond, to consider their positions.
"I'm like everybody else in this in that now that the chairman of Barclays has fallen on his sword and has taken responsibility for what has happened, everybody is asking when are the other senior people at the top of Barclays going to take responsibility for the things that happened on their watch," the Lib Dem leader said on Monday.
"I don't think it is for politicians to individually hire and fire bankers, but I do think the buck stops at the top."
More to follow.