Ed Miliband has called for a criminal investigation into Barclays after the bank was fined £290 million for manipulating interest rates.
In a speech on Thursday morning, the Labour leader said a "slap on the wrist" was not enough
"When ordinary people break the law, they face charges, prosecution and punishment," he said.
"We need to know who knew what when, and criminal prosecutions should follow against those who broke the law."
He added: "The public who are paying the price for bankers’ irresponsibility will expect nothing less."
Miliband also said the government needed to urgently look at the regulation of the banks to ensure it could not happen again.
"This shines a light on a swaggering culture which is not about serving the public, but serving itself by whatever means necessary," he said.
"Too many people in the banks clearly think they were big to fail, too powerful to be challenged.
"They clearly believed they could do anything they liked and were above the law.
"This is yet another example of some of the rich and powerful having their own moral standards, just as we saw during phone hacking."
David Cameron said the “whole management team” at Barclays “have got some serious questions to answer” in the wake of the scandal.
The penalties from UK and US regulators, including a record £59.5m 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.
Bob 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."
After one submitter of information responded favourably to a trader's request to lower a closely-watched interest rate, the trader came back: "When I retire and write a book about this business your name will be written in golden letters."
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.
Barclays is the first major financial institution to settle with regulators following a wide-ranging probe that has spanned North America and Europe.
Diamond said: "I am sorry that some people acted in a manner not consistent with our culture and values.
"The events which gave rise to today's resolutions relate to past actions which fell well short of the standards to which Barclays aspires in the conduct of its business.
"Nothing is more important to me than having a strong culture at Barclays."
The chairman of the Commons Treasury Committee, Andrew Tyrie, said they would now be summoning 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.
Tyrie told Channel 4 News: "The crucial thing now is to make sure that it is being cleared up. That is why we will be calling in Bob Diamond to make sure that what's required had been done in Barclays to improve the culture."