A former chief executive of UBS, Marcel Rohner, has blamed "mercenaries" for the Swiss bank’s role in the global interest-rate rigging scandal, media reports said.

UBS was fined a record $1.5 billion in December last year for its involvement in manipulating LIBOR interest rates, becoming the second major bank, after Barclays, to have been punished for the affair. (In the case of Barclays, the scandal led to the resignation of its high-flying CEO, Robert Diamond.) Zurich-listed UBS, which has been looking to revive its fortunes after suffering major losses in the credit crunch, in late 2011 also disclosed $2.3 billion of losses caused by a rogue trader in a separate affair. The trader has been subsequently convicted and jailed.

As far as the latest affair is concerned, Rohner told the Parliamentary Commission on Banking Standards yesterday: "In these pockets where we had these problems it wasn't probably a bad culture, but it was a lack of culture.”

"When you grow a business too quickly you hire people from many different places and some of them ... you really have to qualify as mercenaries," he told the panel of lawmakers, according to a report by Reuters.

Panel members reportedly accused Rohner and three other former UBS executives of gross negligence and incompetence for failing to detect the manipulation, which stretched back to 2005 and occurred when each of them had been in charge of the bank's investment business.

"The level of ignorance seems staggering to the point of incredulity," Andrew Tyrie, who heads up the PCBS, was quoted as saying. "Not only were you ignorant of what was going on, but you were out of your depth," he said.

All four executives said the first they had heard of UBS' involvement in rigging the inter-bank interest rate system was from press reports in 2011.

To view a recent WealthBriefing editorial on the implications for UBS, click here.