Swiss bank UBS has been fined £940 million by regulators for "extensive and widespread" attempts to rig interbank lending rates.
The bank agreed the settlement after admitting to fraud and corrupt payments to brokers as it sought to manipulate Libor rates to flatter its own financial strength and reputation.
The fine, which includes a record £160 million penalty from the UK's Financial Services Authority, marks the biggest yet from the industry's Libor-rigging scandal and is far larger than the total of £290 million paid by Barclays for Libor manipulation this summer.
The FSA said the misconduct was rife throughout the bank between 2005 and the end of 2010 as UBS traders routinely made requests to colleagues responsible for determining Libor and Euribor submissions in an effort to benefit their own trading positions.
It said that at least 45 individuals including traders, managers and senior managers were involved in, or aware of, the practice. The regulator recorded at least 2,000 requests for inappropriate submissions and said many more would have been made orally.
The FSA said misconduct at UBS was "all the more serious" as it had attempted to manipulate Libor submissions at other banks, making corrupt payments to reward brokers for their efforts. It made corrupt payments of £15,000 a quarter to brokers over at least 18 months, according to the FSA.
Sergio Ermotti, chief executive of UBS, said the group had "taken decisive and appropriate actions" following the probe. He added: "We deeply regret this inappropriate and unethical behaviour. No amount of profit is more important than the reputation of this firm, and we are committed to doing business with integrity."
Libor is the umbrella term for benchmark rates that underpin the terms of 500 trillion US dollars of contracts from mortgages to the cost of corporate lending.
As well as the FSA, UBS said it had also agreed to pay 1.2 billion US dollars (£737 million) in combined fines to the US Department of Justice and the Commodities Futures Trading Commission, and 59 million Swiss francs (£40 million) to UBS's main Swiss supervisor, the Swiss Financial Market Supervisory Authority.
UBS said the fines were likely to see it report a loss of around 2 billion to 2.5 billion Swiss francs (£1.3 billion to £1.7 billion) for the fourth quarter. The Zurich-based bank, which has around 6,500 staff in London, has endured a turbulent year after the jailing of rogue trader Kweku Adoboli.