More banks face interest rate rigging investigation
A number of banks are being investigated and could face sanctions after Barclays was fined £290m ($450m) for trying to manipulate interest rates at which banks lend to each other.
Regulators in Europe, the US and Asia have said that investigations into other banks are "ongoing".
The UK's Financial Services Authority said the early signs were that Barclays had not been the only firm involved.
Barclays has said its actions "fell well short of standards".
Its traders lied to make the bank look more secure during the financial crisis and, sometimes - working with traders at other banks - to make a profit.
Chief executive Bob Diamond and three other top executives at the bank are to give up their bonuses this year.
Tracey McDermott, director of enforcement at the FSA, which imposed fines alongside the US financial regulator, told the BBC: "We have a number of investigations that are ongoing.
"Obviously we need to look at each case on its own particular facts but the initial indications are that Barclays was not the only firm that was involved in this."
The US Department of Justice also said criminal investigations into "other financial institutions and individuals" was ongoing.
Other big names believed to be under investigation include Citigroup, JP Morgan, Deutsche Bank, HSBC and Royal Bank of Scotland.
Barclays' misconduct relates to the daily setting of the London Interbank Offered Rate (Libor) and the Euro Interbank Offered Rate (Euribor).
These are two of the most important interest rates in the global financial markets and directly influence the value of trillions of dollars of financial deals between banks and other institutions.
They can also affect lending rates to the public, for instance with some mortgage deals.
It is not yet clear whether Barclays staff actually succeeded in manipulating the interest rates to the bank's advantage and therefore whether it had any impact on borrowers.
While the FSA said only that the Barclays employees had attempted to do so, the US Department of Justice said that on some occasions they did affect the Libor and Euribor rates.
Former City minister Lord Myners told the BBC's Newsnight that any Barclays staff responsible for manipulating the Libor rate should face the prospect of going to prison.
He said the behaviour of Barclays staff was the worst he had seen.
"This is the most corrosive failure of moral behaviour I have seen in a major UK financial institution in my career," he said.
"I think fines and public criticism will not stop these behaviours. These behaviours will not stop until the people perpetrating it or responsible for overseeing them face the prospect of criminal charges and the prospect of going to jail."
Andrew Tyrie, chairman of the Commons treasury committee, said it would summon Mr Diamond to account for what had happened.
"Banks were clearly acting in concert. I fear it's not going to be the end of the story, that we are going to find that other banks have been involved," he said.
The fine imposed on Barclays is part of an international investigation into the setting of interbank rates between 2005 and 2009.
Each day the British Bankers' Association (BBA) and the European Banking Association publish the Libor and Euribor rates by taking an average of the estimated rates submitted to them by leading banks.
Between 2005 and 2008, the Barclays staff who submitted estimates of their own interbank lending rates were frequently lobbied by its derivatives traders to put in figures which would benefit their trading positions, in order to produce a profit for the bank.
And between 2007 and 2009, during the height of the banking crisis, the staff put in artificially low figures, to avoid the suspicion that Barclays was under financial stress and thus having to borrow at noticeably higher rates than its competitors.
The FSA pointed out that Barclays traders were quite open about their routine attempts to lobby their colleagues who submitted the bank's estimate of its borrowing costs to the BBA.
It was particularly concerned because it appeared to be "accepted culture" among some staff.
"Requests to Barclays' submitters were made verbally and a large amount of email and instant message evidence consisting of derivatives traders' requests also exists," the FSA said.
In one instance, a trader recounted a conversation in which he had "begged" the submitter to put in a lower Libor figure.
"I'm like, dude, you're killing us," he said. His manager replied, "just tell him to... put it low".
In turn, the staff submitting the data would respond to the traders' requests.
"For you…anything," said one. "Done… for you big boy," said another.
And: "I owe you big time... I'm opening a bottle of Bollinger."