The chastened former head of Barclays apologized for the "reprehensible" behavior of his traders who fixed interest rates, but told British lawmakers on Wednesday his bank had been unfairly singled out after coming forward to admit wrongdoing.

Bob Diamond, 60, quit this week after Barclays agreed to pay nearly half a billion dollars in fines for manipulating the interest rates at the heart of the global financial system.

British politicians have seized on the case as a symbol of a culture of greed that has poisoned the entire financial industry.

Newspapers have highlighted e-mails disclosed in the case which show traders congratulating each other for fiddling figures with promises of bottles of champagne.

Appearing thoughtful and humble before an often hostile parliamentary committee, the man who until Tuesday was one of the world's highest paid and most powerful financial executives with an aggressive reputation acknowledged "inexcusable" behavior among his group's traders.

"When I read the e-mails from those traders, I got physically ill," Diamond said. "That behavior was reprehensible, it was wrong. I am sorry, I am disappointed and I am also angry."

He said those involved in rigging interest rates would be subject to criminal investigation and should be "dealt with harshly".

The wrongdoing at the 300-year-old bank was "not representative of the firm that I love so much", the American banker said, appearing on his nation's Independence Day.

But he insisted that Barclays was being made a scapegoat because it had cooperated with the authorities to help unearth the misdeeds.

"This week the focus has been on Barclays because they were the first," Diamond said, describing years of cooperation with regulatory agencies to uncover the practice.

"I think it's a sign of the culture of Barclays that we were willing to be first, we were willing to be fast and we were willing to come out with this."

The decision by Britain's third-biggest bank to cooperate with regulators may have been designed to limit damage but it appeared to have backfired, hurting Barclays' reputation and costing Diamond his job, banking analysts said.

It may also discourage other banks from cooperating with regulators.

The case has reopened a debate in Britain on whether big banks should be split into retail and investments units, while also raising questions about the morality of bankers' salaries and bonuses and whether banks should be more closely regulated.