Bob Diamond tonight angrily rejected suggestions that he misled MPs over regulators' concerns about activities at Barclays.
The bank's former said the claims were "totally unfair and unfounded" - and indicated he was ready to appear before the Commons Treasury Select Committee again to defend his reputation.
ITV News' Political Correspondent Lucy Manning reports:
The rejection of the claims came in a letter sent following an evidence session with Barclays chairman Marcus Agius.
"Having watched the committee's session today I was dismayed that you and some of your fellow committee members appeared to suggest that I was less than candid with the committee last week," he wrote.
"Any such suggestion would be totally unfair and unfounded."
Here is the letter Mr Diamond sent to Treasury Select Committee chairman Andrew Tyrie.
During the dramatic session, Mr Agius disclosed that Mr Diamond was "voluntarily" waiving a potential £20 million in deferred share bonuses.
But the ex-chief executive will walk away with a £2 million package, made up of a year's salary and pension cash contribution, after quitting.
Mr Agius - who has signalled he will step down after a replacement for Mr Diamond is found - admitted that Barclays' relationship with the regulator was "strained".
The MPs cited a letter from the Financial Services Authority (FSA) flagging the regulator's concerns about "a pattern of behaviour" in which Barclays sought to gain advantage through the use of complex structures which are "at the aggressive end of interpretation of the relevant rules and regulations".
Committee chairman Andrew Tyrie and other members insisted the evidence contradicted what they heard from Mr Diamond, who denied knowing that regulators were concerned.
Many of us when we heard that last week thought that his replies were implausible but didn't have evidence to support that hunch. Today we began to collect quite a bit of evidence to suggest that Bob Diamond's presentation of what happened was quite a long way away from what really happened.
Labour member John Mann said Mr Diamond had "serially misled" Parliament on a range of issues.He said it was the majority view of the committee that Mr Diamond should be recalled.
Mr Mann - who is also pressing for Mr Diamond to donate his £2 million pay- off to charity - added: "There's a question of the reputation of Parliament."
In his letter responding to the allegations, Mr Diamond stressed that he had not been questioned about the period when the FSA had raised concerns, in April this year.
"I trust this addresses any concerns you may have had," he went on. "The comments made at today's hearing have had a terribly unfair impact upon my reputation, which is of paramount concern to me. I look forward to discussing this issue with you further if you wish to do so."
Mr Agius also revealed that Sir Mervyn called him into an emergency meeting to explain "in no uncertain terms" that the FSA believed Mr Diamond needed to go.
"The public outcry had been far greater than thought," said Mr Agius.
He said it was clear from the meeting with Sir Mervyn that the FSA thought Mr Agius's resignation was inadequate and that further action was necessary.
But he argued the FSA had changed its stance on Mr Diamond's position at the helm in the days after the rate-rigging scandal broke.
He said the regulator did not give the impression Mr Diamond should resign when the bank's Libor fixing settlement was first announced the previous week.
In a fierce exchange with the committee, one MP said: "A great British bank has been dragged through the mud - are you ashamed?"
Mr Agius replied: "I regret deeply what's happened to Barclays. I'm truly sorry."
He said the board "welcomed" the move by Mr Diamond to forgo his long-term bonus incentives.Details of his pay-off follow what are said to have been intense negotiations over Mr Diamond's leaving deal.
It is thought Barclays remains in talks with Mr Diamond's right-hand man, chief operating officer Jerry del Missier, over his pay-off.
Mr Diamond said he hoped the agreement "will help close this chapter and allow Barclays to move forward and prosper" after the bank was fined #290 million for attempting to fix the interbank borrowing rate Libor.
Prime Minister David Cameron's official spokesman said: "I think the decision to forgo the bonus is a sign that they understand public concerns and that they understand that there is a need for a change in the culture of banks."
Mr Diamond added in a statement: "For the past 16 years I've had the honour of working at Barclays."The wrongful actions of a relative few should not detract from the outstanding work that Barclays employees carry out each day on behalf of clients and customers around the world."
Mr Diamond has a six-month notice period, but is getting a year's salary as a pay-off because he is making himself available to Barclays.
The former chief executive was thought of highly by shareholders and clients, according to Mr Agius.
He said: "The board deeply regrets the circumstances that led to Bob resigning his positions at Barclays.
"Despite having no personal culpability, he recognises more than anyone the negative attention that they have generated and has taken characteristically strong action to address that," he added.
The former Barclays chief executive quit last Tuesday as the full scale of the scandal emerged.
He said in an appearance in front of MPs last Wednesday he felt "physically ill" when he discovered traders at his bank were manipulating the inter-bank rate.
Mr Agius was the third high-profile witness to appear before the Committee since last week as MPs sought to get to the bottom of the Libor scandal that has rocked the banking industry.
Bank of England deputy governor Paul Tucker appeared in front of the Committee yesterday and said he "absolutely" rejected suggestions he had leant on Barclays to manipulate a key lending rate or that Labour ministers had encouraged him to do so.