Bob DiamondBank of England deputy governor Paul Tucker has 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 on Tuesday, to the then-chief executive John Varley and his right-hand man 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. But the Prime Minister joined calls for bank chiefs forced out because of the scandal to be denied huge payoffs.

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.

Barclays said there was no allegation by the authorities that this instruction was intended to manipulate the ultimate Libor rate. The Financial Services Authority investigated Mr del Missier personally in relation to these events and closed the investigation without any enforcement action, the statement added.