Former Barclays chief executive Bob Diamond criticized \"reprehensible\" behavior over a rate-fixing scandal yesterday in his first public comments since quitting amid a high-profile boardroom exodus. Diamond added that while there had been \"mistakes\" at the lender, swift action was taken to tackle traders\' attempts to manipulate key inter-bank lending rates. \"Clearly there were mistakes, clearly there was behavior that was reprehensible,\" the American banker told the British Parliament\'s Treasury Select Committee. The former boss of Barclays said that his bank illegally reported low borrowing rates in October 2008 because other banks were reporting even lower ones, making Barclays look bad and threatening efforts to attract investment from Qatar. Diamond stepped down as chief executive this week, as did the chairman and chief operating officer. On Oct. 29, 2008, Diamond had a conversation with Paul Tucker, deputy governor of the Bank of England, in which Diamond raised concerns that other banks were reporting false lower rates. He said he was \"physically ill\" when he learned the full detail of the revelations, which he insisted was only after the regulators\' investigation this month. \"I\'m sorry, I\'m disappointed and I\'m also angry,\" Diamond said.