Bob Diamond blamed a "series of unfortunate events" for his shock departure from Barclays as he fended off calls to give up his multimillion-pound bonuses.
The banking chief admitted feeling "physically ill" when he discovered traders had fiddled the key Libor rate but denied he was "personally culpable" for their actions.
Mr Diamond shed more light on a phone call he had with Bank of England deputy governor Paul Tucker about concerns "officials within the government" had with the Barclays high Libor rates.
As the American banker admitted Barclays lowered the rates amid fears the Government wanted to nationalise the lender, Chancellor George Osborne claimed members of Gordon Brown's administration were "clearly involved".
The 60-year-old was hauled before the Treasury Select Committee after Barclays was fined £290 million by UK and US regulators for fixing the Libor which affects loans and mortgages everywhere.
Dressed in a blue suit and green spotted tie, he opened the session by declaring his "love" for Barclays and added: "At the core of the issues there clearly were mistakes, clearly there was behaviour that was reprehensible."
He repeatedly stated traders' behaviour was "wrong" and that he was "disappointed", "angry" and "sorry". He added: "This was wrong. I'm not happy about it."
But when faced with questions over his exit pay or clawback of his bonuses, he was more evasive, saying: "That is a question for the board."
In a bruising exchange, Bassetlaw MP John Mann pushed Mr Diamond to give up millions of pounds he could be due in shares.
Challenged that not having known about the abuses amounted to gross incompetence, Mr Diamond stressed that the investigation he had put in place was "market leading".