© Dylan Martinez/Reuters
Calls for Bob Diamond to resign as CEO of Barclays are growing becoming more vociferous.
The head of the Institute of Directors (IoD) led the mounting clamour on Friday from the City, business leaders and politicians for a cull at the top of Britain's banks. In an unusually strong condemnation of the culture of banking, Simon Walker, director general of the IoD, said it was "high time" for a clearout of top bankers after a wave of mis-selling scandals and market manipulation.

His remarks came on a day when pressure was mounting on Bob Diamond to step down as chief executive of Barclays in the wake of the record-breaking £290m fine for the bank's attempt to fix a crucial interest rate and as the Financial Services Authority ordered Barclays and three other high street banks to compensate up to 28,000 small businesses that were mis-sold products designed to minimise their risk against interest rates going up.

A 10-day computer meltdown at Royal Bank of Scotland, which left up to 13 million customers unable to get their current account balances, hardened attitudes among the public and politicians that the clean-up exercise from the 2008 banking crisis still had a long way to go.

David Cameron, Sir Mervyn King, governor of the Bank of England, Lord Turner, chairman of the Financial Services Authority, business secretary Vince Cable and Ed Balls, the shadow chancellor, all queued up to condemn the culture in the City.

Despite the 2008 bailout of the banks, the City has fended off the root and branch reform favoured by King because of a powerful lobbying campaign that emphasised its pivotal role in the UK economy. But that argument has been turned on its head in the past 72 hours by the extraordinary revelations about systemic bad practice among traders in setting interest rates known as the London interbank offered rate (Libor).

Now the argument is that Britain's vital interests in financial services can only be protected by a restoration of trust that demands a shakeout of the management of the banks. The strongest condemnation came from Walker, who was infuriated by the abusive treatment of small firms with the mis-selling of interest rate swaps.

"This mis-selling is an outrageous scandal, which has cost many people their livelihoods and caused huge distress for many more. The regulator must ensure there are severe consequences for those responsible. As well as ripping off their customers, they have also harmed the reputation of business as a whole - they should feel deep shame for the damage they have done.

"This news, combined with the exposure of abusive Libor rate manipulation, demonstrates that there is a serious failure of leadership in many of the banks. It is high time for a clearout of the leaders who created this mess, and they should be replaced with new blood," he said.

The call for change is not the first since the financial meltdown began almost five years ago with the credit crunch and the run on Northern Rock. In the autumn of 2008, there were calls for change at the top after the government bailed out RBS, Lloyds and HBOS to prevent them from collapsing. The culture of big pay deals never changed and has been a nagging sore for voters as a tentative recovery in the economy has been aborted and Britain has slipped into a double-dip recession.

Many of the leaders of that era have gone, and the interest rate manipulation took place under a previous regime. Nevertheless, for those calling for Diamond's scalp, the key point is that he was running the division of Barclays that was caught up in the scandal.

More broadly, the revelations this week have scuppered any efforts by the banks to water down the forthcoming legislation to ringfence retail banks from the "casino" investment banks, as recommended by Sir John Vickers.

Vince Cable, the business secretary, said: "This mis-selling scandal is an urgent and immediate problem the government has got to tackle. We are trying to clear up a massive cesspit and we have got to deal with it through tough regulation, through taxation and through this crucially important bit of legislation separating out the casinos, the investment banks, from the ordinary retail banks."

Cable said the mis-selling of interest rate-hedging products to businesses such as fish and chip shops and butchers was "very, very cynical". "Businesses were being told they could only have a bank loan if they bought one of these products and a lot of these companies are now being ruined on the back of this," he said.

Lord Oakeshott, the Liberal Democrat peer and campaigner for bank reform, said: "No one knows better than the governor [of the Bank of England] the risk we run every day that passes until we break up the banks. Passing Vickers into law is a top priority for parliament to make banks safe and take taxpayers' guarantees away from greedy gamblers like Bob Diamond."

The complete separation of high street banks from investment banks has so far been avoided. The ringfencing move was a less bad option for the banks, which argue they can operate more efficiently by uniting all their businesses under one roof.

Banks may now feel that the current Vickers proposals are the best they can hope for now the views expressed by Walker are being echoed by investors in the City as well as their traditional critics.

"Bankers need to be very clear that the old culture of sharp practice and playing fast and loose with the rules is not acceptable. The challenges facing the banks remain considerable and now is the time for responsible leadership. We need to rebuild a banking system that is robust, credible and trusted," said Iain Richards, head of governance and responsible investment at Threadneedle.

Tony Greenham, the head of finance at the New Economics Foundation thinktank, said: "Trust is at the very core of banking. This is a perfect manifestation of what has been taking place over the past 10 or 20 years: a progressive erosion of the values of the City. Banking only works if you put the customer first. Honesty and integrity have to guide everything you do, and that may not be the way to maximise your bonus, or your short-term profits."