LITTLE ROCK — Royal Bank of Scotland on Wednesday became the third international bank to reach a settlement in the ongoing investigation of the widespread manipulation of the global interest rate known as the London interbank offered rate, or Libor.

Federal prosecutors and regulators said RBS has agreed to pay $612 million to U.S. and British authorities for its role in the rate fixing scandal. As part of the deal, the bank’s Japanese subsidiary pleaded guilty to criminal charges of wire fraud and entered into a deferred prosecution agreement with the U.S. Justice Department. No individuals have been indicted.

The bank admits to scheming to manipulate rates, either keeping them artificially high or low, to increase profits from its derivatives and money market trading activities as far back as 2006. Authorities say more than a dozen RBS traders around the world engaged in this illegal activity, even after they learned that regulators were investigating Libor in 2010.

“It is amazing that RBS employees tried to fly above the law. They acted as if they were the masters of the universe and the rules of fair play just didn’t apply,” said Bart Chilton, a commissioner at the Commodity Futures Trading Commission.

The commission was the first to uncover evidence that something was amiss with the rates going as far back as 2005.

Libor serves as a standard interest rate for loans between banks and as a benchmark for more than $360 trillion in lending to businesses and consumers.

At the height of the 2008 financial crisis, 16 financial institutions, including Bank of America, HSBC and JPMorgan, submitted data to set the daily Libor. That information was collected on behalf of the British Bankers’ Association by Thompson Reuters, which calculates the averages and devises the Libor.

Critics of the system say there is not enough transparency in how banks set their daily rates, which leaves the process open to fraud. Regulators on both sides of the Atlantic are considering ways to improve the system, although much of the world’s financial markets continue to use the rate.

Authorities say RBS was part of a larger conspiracy to fiddle with Libor and the Euro interbank offered rate, or Euribor. Traders at the bank worked in concert with their counterparts at UBS to manipulate Swiss Franc Libor, according to the Commodity Futures Trading Commission order.

RBS agreed to pay $325 million to the commission and another $137 million to Britain’s Financial Service Authority for its actions. The bank will also hand over $150 million to the Justice Department.

In a statement, RBS Chairman Philip Hampton said “this is a sad day” for the bank and acknowledged that “there were serious shortcomings in our systems and controls and also in the integrity of a small group of our employees.”

All 21 employees implicated in the investigation have either faced disciplinary action or left the bank without a bonus and full claw-back of any outstanding past bonus awards. The head of the markets and international banking division, John Hourican, has also resigned from his position. While officials at RBS say Hourican had no knowledge of the rate-rigging scheme, his departure is in recognition that management failed to detect the problem.

“We have to fix the culture in the banking industry,” Hampton said. “The most important part of that is ... acting with integrity. And it also involves facing up to the Bank’s past failings, no matter how uncomfortable that is.”

The Justice Department has faced intense scrutiny ofits handling of financial firms accused of breaking the law. Critics say the agency has fallen short of its duties by failing to put any senior executives behind bars. But the department contends that it has to consider the potential effect of criminal indictments on the health of the firms and the overall financial system.

Barclays was the first bank to confess its role in the ratefixing scandal in June, when it agreed to pay $450 million to settle allegations. Swiss banking giant UBS followed its lead in December by reaching a $1.5 billion settlement with global authorities, which included the indictment of two of its traders and a guilty plea by its Japanese subsidiary.

Business, Pages 25 on 02/07/2013