More banks could be caught in the scandal which saw Barclays pay £290 million to settle claims that it used underhand tactics to try to rig financial markets.
The Financial Services Authority (FSA) disclosed that it had a number of other investigations under way in the wake of the allegations that Barclays manipulated the rates at which banks lend to each other.
"We have a number of investigations that are ongoing," Tracey McDermott, the FSA's acting director of enforcement and financial crime, told BBC's Newsnight. "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 chairman of the Commons Treasury Committee, Andrew Tyrie, said they would now be summoning Barclays chief executive Bob 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 penalties from UK and US regulators, including a record £59.5 million fine from the Financial Services Authority (FSA), followed claims Barclays manipulated the Libor and Euribor interbank lending rates.
In the depths of the financial crisis, Barclays gave false information about the interest rates it had to pay to borrow money in an effort to paint a false picture of its health to markets.
Mr Diamond, who was in charge of Barclays Capital at the time the breaches occurred between 2005 and 2009, apologised and said he and three other key executives would waive their bonuses for this year.
A trail of emails and messages disclosed by the FSA showed how traders broke so-called Chinese Walls, which are designed to avoid conflicts of interest within financial firms, as they requested Barclays make changes to the Libor rate in a bid to boost their profits.
In one request for a change to the Libor rate, a trader said: "Coffees will be coming your way either way, just to say thank you for your help in the past few weeks". To which the Barclays submitter responded: "Done, for you big boy."
The scandal is another blow to the beleaguered banking sector as it battles to restore its tarnished image in the wake of the financial crisis, the scandal of mis-sold PPI and the computer problems at RBS which froze millions out of their accounts.
10 things we hate about our banks
More banks probed over rate rigging
More than 46,000 of 106,000 the complaints received by the FOS in the second half of last year related to payment protection insurance (PPI). And the organisation is expecting to receive a record 165,000 PPI complaints in 2012/2013.
The huge numbers are due to the PPI mis-selling scandal that should now be a thing of the past, but there is no doubt that the insurance, which can add thousands to the cost of a loan, is highly unpopular!
(Pictured: Martin Lewis after the PPI payout ruling)
Complaints about mortgages jumped by 38% in the last six months of last year, the FOS figures show, compared to an increase of just 5% in investment-related complaints.
Common gripes about mortgages include the exit penalties imposed should you want to sell up or change you mortgage before a fixed or discounted deal comes to an end, and the high arrangement fees charged by many lenders.
While there is nothing in the data released by the FOS about the number of complaints relating to savings accounts, hard-pressed savers have been struggling with low interest rates for several years now.
You can get up to 3.10% with Santander's easy-access eSaver account, but many older accounts are paying 1.00% or less and even this market-leading offer includes a 12-month bonus of 2.60% - meaning that the rate will plummet to just 0.50% after the first year.
Banks are imposing the highest authorised overdraft interest rates since records began, with today's borrowers paying an average of 19.47%, according to the Bank of England.
A typical Briton with an overdraft of £1,000 is therefore forking out around £200 in interest charges alone. Coupled with meagre returns on savings, it's enough to make your blood boil!
While authorised overdrafts may seem expensive, going into the red without permission will cost you even more due to huge penalty fees.
Barclays, for example, charges £8 (up to a maximum of £40 a day) each time that there is not enough money in your account to cover a payment.
If you need to send money abroad, the likelihood is that your bank will impose transfer charges - and offer you a poor rate of exchange. Someone transferring a five-figure sum could easily lose out by £500 or more as a result.
The good news, however, is that you can often get a better deal by using a currency specialist such as Moneycorp.
Automated telephone banking systems, not to mention call centres in far-flung parts of the world, are one of our top gripes - especially as we often encounter them when we are already calling to report a problem.
In the words of one disgruntled customer: "What is it about telephone banking that turns me into Victor Meldrew? Well, maybe it's the fourteen security questions, maybe it's the range of products that they try to push or maybe it's because I'm forced to listen to jazz funk at full volume while my phone bill soars.
"Actually though, I think it's because the people I eventually speak to rarely seem able to solve the issue I'm calling about."
The days of a personal relationship with your bank manager are long gone - for the huge majority of us at least.
When ethical Triodos Bank investigated recently why around 9 million Britons would not recommend their banks to a friend or relative, it found that almost a third felt they were not treated as individuals. Another 40%, meanwhile, were simply disappointed with the customer service they received.
When you're in a rush, the last thing you want to do is wait in a long queue at your local branch.
Researchers at consumer champion Which? recently found that most people get seen within 12 minutes, but you could have a much longer wait if you go in at a busy time. Frustrating stuff!
The Triodos Bank research also indicated that the bonus culture that ensured the bank's high-flying employees received large salaries, even when it was making a loss at the taxpayer's expense, was hugely unpopular with consumers.
About a quarter of those who would not recommend their current banks said this was the main reason why. And with RBS executives sharing a £785 million bonus pool despite the bank, which is 82% publicly owned, making a loss of £2 billion last year, it's not hard to see why.