Barclays was fined a record £290m by UK and US regulators for attempting to rig the Libor inter-bank lending rate reports The BBC.
The apology came as the bank’s adjusted pre-tax profit for the first six months of 2012 rose 13 per cent to £4.2bn.
It set aside £450m to cover potential costs of providing redress to small businesses sold inappropriate swaps.
On a statutory basis, profit before tax fell 71% to £759m after taking a £2.9bn charge for having to account for the value of its own credit.
“We are sorry… and recognise that we have disappointed our customers and shareholders,” said chairman Marcus Agius.
“I speak for all of Barclays people when I say how determined we are to regain the full confidence of all our stakeholders; customers and clients, investors, regulators and staff alike.”
The Libor scandal led to the resignation of chief executive Bob Diamond.