UBS is refusing to discipline traders who used chat rooms that gave clear details of their colleagues' plans to fix Libor interest rates, for which the bank paid $1.5bn (£940m) in fines.
The Parliamentary Commission on Banking Standards was told today that the bank had fired 18 traders who were directly involved, with a further 22 having left the bank before the scandal broke.
But Andrew Williams, the Swiss bank's global head of compliance, told astonished members that more than 30 people who were known to have used the same internal bank chat rooms would not face sanction because the bank could not be sure they had known what was going on.
He said: "Disciplinary action has not been taken simply because someone puts something on a chat channel someone is a member of. It would be harsh to impute knowledge simply by it being there. It would be like something in a newspaper. You wouldn't necessarily read it."
Later he added: "We don't know how many people saw the message."
But Mark Garnier, the Tory MP and former investment banker, questioned whether this could really be the case. He argued that "someone good at his job as a trader should know all what is going on".
Mr Williams also admitted the bank was powerless to "claw back" bonus payments from those who had left, including Tom Hayes, who moved to Citi and who has since been indicted in the US.
Andrew Tyrie, the chairman of the commission, and other members were sceptical whether just 18 dismissals could be enough to reform a culture that had allowed such a scandal to take place under senior managers' noses. He described it as "a shocker of enormous proportions".
Lord Lawson, the former Chancellor, described what went on at the bank as "crookery" adding: "How many [of the sacked traders] have you named so any other bank would know? Or do you discretely let them go so they can discretely take their crookery elsewhere?" He was told the FSA had a list of names.
UBS's new head of investment banking, Andrea Orcel, told MPs reforming the bank's culture was "a work in progress" but he was "absolutely determined" to root out the cancer that had grown at the bank.
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