Bank of England deputy governor Paul Tucker today requested to appear before MPs “as soon as possible” to clear up his role in the rate-fixing scandal.
Ahead of his own meeting with the Treasury Select Committee, former Barclays boss Bob Diamond released a record of a phone call with Mr Tucker discussing the key interest rate at the centre of the unfolding affair.
The note sent by Mr Diamond, who resigned with immediate effect yesterday, to the then-chief executive John Varley and his right-hand men Jerry del Missier ultimately led to Barclays staff pushing down the interbank lending rate, known as the Libor.
A statement from the Bank of England said: "Mr Tucker is keen to give evidence to the committee in order to clarify the position with regard to the events involving the Bank of England, including the telephone conversation with Bob Diamond on October 29, 2008."
Mr Diamond's dramatic disclosure has raised questions over the involvement of the central bank, Whitehall and the last Labour government in the rate-fixing affair that has shaken the banking industry to its core.
MPs have warned that rate-rigging took place by rogue traders long before the contentious conversation in October 2008 and will demand to know how this was allowed to happen on Mr Diamond's watch.
The Treasury Select Committee is expected to confirm whether Mr Tucker or any other members of the BoE will be required to give evidence after Mr Diamond's appearance.
As the American banker prepares a rigorous defence of his actions, the details of his exit package are still being thrashed out with reports that he will be asked to hand back nearly £20 million of unvested share awards.
The Prime Minister joined calls for bank chiefs forced out because of the scandal to be denied huge payoffs.
"It would be completely wrong if people who were leaving under these circumstances were given some vast payoff," he told MPs.
"It would be completely inexplicable to the British public and would not be right. I very much hope that does not happen."
Mr Diamond is expected to "speak more freely" when he gives evidence now he is no longer at the helm of Barclays, with much focus on the chat between the bank chief and Mr Tucker about Libor rates at the height of the credit crunch in 2008.
In a note, Mr Diamond said Mr Tucker relayed concerns from "senior Whitehall figures" over why Barclays was always towards the top end of Libor pricings.
He is alleged to have added that the bank's Libor rate did not "always" need to appear as high as it had recently.
According to Barclays, Mr Diamond "did not believe he received an instruction from Paul Tucker or that he gave an instruction to Jerry del Missier".
"However, Jerry del Missier concluded that an instruction had been passed down from the Bank of England not to keep Libors so high and he therefore passed down a direction to that effect to the submitters," a statement said.
Barclays said there was no allegation by the authorities that this instruction was intended to manipulate the ultimate Libor rate.
The FSA investigated Mr del Missier personally in relation to these events and closed the investigation without any enforcement action, the statement added.
However, Mr del Missier followed Mr Diamond out of the door yesterday and quit with immediate effect.
Conservative MPs highlighted the reference to pressure from Whitehall, suggesting that Labour ex-ministers had to explain their involvement.
Labour's former City minister Lord Myners said he did not think any of his Treasury colleagues, under the leadership of Alistair Darling, discussed the rate with the Bank of England.
But Lord Myners said: "We were not interested in the Libor-setting process, let alone the submissions by individual banks. I don't think it was on our agenda. I don't remember it being discussed at all."
Alistair Darling, who was chancellor from 2007 to 2010, said yesterday he did not believe anyone at the Treasury would have urged such improper intervention by the BoE.
However, he appeared to stop short of expressing confidence that no one in government would have done so.
"Firstly, I think it is important that this committee which is examining Bob Diamond tomorrow also gets Paul Tucker in front of it at the earliest possible opportunity. Because this is Bob Diamond's account," Mr Darling said.
Shadow chancellor Ed Balls, a close ally of Gordon Brown and a Treasury minister in 2006/07, insisted he knew nothing about the issue.
"I have absolutely no idea, that's why I want, as Ed Miliband does, a full open judicial inquiry at arm's-length forensically to ask these questions to see whether anybody knew what was going on," he said.
The Treasury Select Committee is expected to decide whether to call Mr Tucker - who has been widely tipped as the next head of the Bank of England - after Mr Diamond's evidence.
Mr Osborne, who announced a parliamentary probe into banking standards on Monday, said Mr Diamond's resignation had been the "right decision" for the bank and for the country.
The Treasury launched a consultation on the possibility of introducing a new criminal offence covering serious misconduct in bank management.
Labour leader Ed Miliband continued to press the Prime Minister to stage a two-part judicial inquiry into the banking scandal but Mr Cameron resisted the calls.
Mr Diamond is estimated to have received £120 million since joining Barclays' board in 2005. He took home nearly £18 million in pay rewards last year.
Deputy Prime Minister Nick Clegg said the public would be "dismayed" if the ex-bank boss walked away with a handsome payoff.
He said: "He has been paid a lot of money over the years so I don't think he's going to be short of a bob or two, and I think many people will be dismayed that, as he is leaving under a cloud, he might be paid handsomely or get handsome rewards for having presided over serious wrongdoing."
The scandal leaves Barclays racing to fill crucial vacancies at its top level. Chairman Marcus Agius, who announced on Monday his own plans to resign, will stay on as executive chairman to lead the search for his replacement and a new chief executive.