Royal Bank of Scotland said on Wednesday it had agreed to pay $612 million (453 million euros) to US and British regulators to settle allegations of trying to rig the key Libor interest rate.
RBS said it had been fined $325 million by the US Commodity Futures Trading Commission, $150 million by the US Department of Justice (DoJ) and £87.5 million by Britain's Financial Services Authority.
The bank has also entered into a deferred prosecution agreement with the DoJ, in relation to one count of wire fraud relating to Swiss franc Libor and one count for an antitrust violation relating to yen Libor.
RBS Securities Japan Limited has also agreed to enter a plea of guilty to one count of wire fraud relating to Yen Libor, the British bank said in a statement.
John Hourican, chief executive of the bank's Markets and International Banking division, is meanwhile to leave RBS.
The investigations uncovered "wrongdoing" by 21 employees, predominantly in relation to the setting of the bank's yen and Swiss franc Libor submissions, the bank said.
"This is a sad day for RBS, but also an important one in continuing to put right the mistakes of the past," Royal Bank of Scotland chairman Philip Hampton said in the statement.
"That is why those responsible have left the organisation or been subject to disciplinary action," he added.
RBS said its derivative traders sought to influence the bank's yen and Swiss franc Libor setters over a period of four years between October 2006 to November 2010.
"Two RBS traders based in London colluded with other banks and brokers in making and receiving requests for higher and lower" rates, it said.
The total fines handed down to RBS are more than those last year slapped on British bank Barclays for Libor rate-rigging, but less than the amount paid by Swiss lender UBS for similar offences.
Libor, or London Interbank Offered Rate, is a flagship instrument used all over the world, affecting what banks, businesses and individuals pay to borrow money. Euribor is the eurozone equivalent.
Libor is calculated daily, using estimates from banks of their own interbank rates, and affects the pricing of more than $300-trillion of contracts across the world, according to British regulator, the Financial Services Authority.But the system has been found to be open to abuse, with some traders lying about borrowing costs to boost trading positions or make their bank seem more secure -- seriously damaging the reputation of the 'City of London' financial centre.
At Swiss bank UBS, two former employees were charged in December when the group's Securities Japan unit settled similar allegations with US and British authorities for $1.5 billion, the biggest amount to date.
The British government owns more than 80 percent of the shares in RBS, owing to a massive £45.5 billion bailout of the bank during the global financial crisis, while there is considerable pressure in Britain for senior bank executives to take responsibility for the Libor crisis.
"Of course the taxpayer shouldn't pay, and nor should the consumers of banks," Britain's Business Secretary Vince Cable told BBC radio on Wednesday.
"If there is a substantial fine it's got to be absorbed by staff in the banks in those bits of the banks that took the excessive risks and created the problem," he added amid calls that RBS should slash upcoming bonus payouts to fund the penalties.
Barclays bank in June agreed to pay about $450 million in connection with the affair, which led to the resignations of three Barclays senior board members, including chief executive Bob Diamond.
More than a dozen other institutions remain under investigation, while last October the British government announced plans to make it a criminal offence to manipulate Libor.