Resigned Barclays chief executive Bob Diamond admitted before the British Parliament that bank personnel may have been involved with low balling or rate fixing since 2005 but insisted that he no direct knowledge of the illegal practices until three years ago.

What happened back then, according to Mr Diamond, "made me feel physically sick," as he described his initial reaction to investigating UK MPs when the wrongdoings started unfurling.

The U.S.-born banker testified a day after he was forced to resign in the aftermath of the $440 million fine slapped by British and U.S. regulators on Barclays last week.

Authorities had determined that Barclays' executives have been trying to manipulate the interest rates that were carried by Libor and Euribor, two global market instruments that serve as gauges for the amount that borrowers pay in servicing debts.

Analysts said Barclays draws direct benefit from the rigging since it creates the impression of stability in the bank, therefore attracting more transactions and increasing the likelihood of more revenues.

To date, 14 traders have been linked by regulatory probes to the scandal, specifically on attempts to lower the rates in Libor between 2007 and 2008 but Mr Diamond claimed that he only got wind of the details in June.

Apparently the practice went on until 2008, allegedly involving senior executives, but Mr Diamond distanced himself from the incidents by telling lawmakers that he was not Barclays head at that time.

He insinuated, too, that Barclays was not the only bank involved in such dealings, pointing to Royal Bank of Scotland (RBS) and Lloyds as likely culpable too with the alleged questionable activities.

These banks, according to the former Barclays CEO, "were all posting at levels they would not have been able to borrow at, had they been able to borrow."

Still, Mr Diamond conceded that "clearly there were mistakes, clearly there was behaviour that was reprehensible," on the part of Barclays.

He asserted, however, that Barclays reacted appropriately and quickly when the scandal broke out.

"The attitude of Barclays three years ago when this was recognised was let's get to the bottom of it," Mr Diamond was reported by Agence France Presse (AFP) as saying on Thursday.

He appeared before the Parliament in the aftermath of the strings of high-profile resignations that rocked Barclays this week, starting off with the departure of company chair Marcus Agius on Monday, which was followed the next day by COO Jerry del Missier.

Following initial hesitations, Mr Diamond also quit on Tuesday, reportedly due to pressures applied by regulators on Barclays' board.