Pressure was mounting on Barclays boss Bob Diamond to step down today following the rate-rigging scandal that has rocked the banking industry.

Shares in the lender were down 8% as Prime Minister David Cameron said the bank had "some serious questions to answer" and Opposition leader Ed Miliband called for a criminal investigation.

Mr Diamond waived his annual bonus for 2012 yesterday after the bank was fined £290 million by US and UK regulators for manipulating the rates at which banks lend to each other to boost its profits.

Lord Oakeshott, a former Liberal Democrat Treasury spokesman, described the bank as "a casino that was rigging the wheels and loading the dice".

"If Bob Diamond had a scintilla of shame, he would resign," he said. "If Barclays' board had an inch of backbone between them, they would sack him."

The controversy, which was illustrated in a series of emails between traders and Barclays staff, could spread to other lenders, including HSBC and taxpayer-backed Royal Bank of Scotland.

Addressing the scandal in a speech to the Unite union conference in Brighton, Mr Miliband said: "This cannot be about a slap on the wrist, a forgoing of bonuses, a fine and that's the end of the matter.

"When ordinary people break the law, they face the full force of the law. The people who have done the wrong thing should face the full force of the law, including criminal proceedings.

"The Government should urgently look at the regulation of banking in this area so this never happens again.

"The wider issue is the culture of the banking industry. This case shines a light on a swaggering culture, about serving itself not the public. Too many people thought they were too big to be challenged - they thought they could do anything they liked. They clearly believed they were above the law."

The penalties from UK and US regulators, including a record £59.5 million fine from the Financial Services Authority (FSA), followed claims that Barclays manipulated the Libor (London Interbank Offered Rate) and Euribor interbank lending rates.

The rates are set on wholesale money markets - where banks lend to each other - which in turn affects rates they pass on to customers through credit cards, loans and mortgages.

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 nothing was more important to him than "having a strong culture at Barclays".

Senior executives Jerry del Missier, Rich Ricci and chief financial officer Chris Lucas will also waive their 2012 bonuses.

A trail of emails, instant messages and phone transcripts disclosed by the FSA showed how traders requested Barclays make changes to the Libor rate 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 payment protection insurance (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 investigation that has spanned North America and Europe.

But Tracey McDermott, the FSA's acting director of enforcement and financial crime, said a number of investigations are still continuing, opening the door to further penalties against banks worldwide.

She said: "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 fine from the FSA would have been £85 million if Barclays had not co-operated.

Barclays also agreed to settle a penalty of 200 million US dollars (£128.2 million) with the Commodity Futures Trading Commission (CFTC) and 160 million US dollars (£102.5 million) to the US Department of Justice (DoJ).

MP John Mann, a member of the Treasury Committee, called for Mr Diamond and RBS chief executive Stephen Hester to be "de-bonused" by taking away the biggest bonus they received over the last three years from their pay.

He said: "Bank bosses have been happy to justify their huge bonuses, claiming it is needed to reward success."

Mr Diamond took a £2.7 million cash bonus last year despite widespread criticism that his pay failed to reflect the struggling performance of the bank. Overall, his package was worth £17.7 million, including a £5.7 million tax payment made on his behalf.

Andrew Tyrie, chairman of the Commons Treasury Committee, said they would now be summoning chief executive Mr Diamond to account for what 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.