Jerry Del Missier, who was president of investment arm Barclays Capital at the time, told staff to lower the key interbank lending rate after misunderstanding Mr Diamond’s account of the conversation with the BoE deputy governor Paul Tucker.
The details of the conversation were disclosed in documents submitted to the Treasury Select Committee ahead of Mr Diamond’s appearance before British MPs tomorrow.
The submission was released after Mr Diamond and Mr del Missier stepped down with immediate effect following increased pressure from politicians, shareholders and former Barclays directors.
Barclays has submitted a copy of Mr Diamond’s note, sent on Oct 30, 2008, to Mr del Missier, and then chief executive John Varley, on his conversation with Paul Tucker, to the Select Committee.
Alison Carnwarth, chairman of the remuneration committee, will ask Mr Diamond, who was awarded a total of £17.7m (€22m) in 2011 alone, to hand back the bonuses, Sky News said.
The speculation comes after proxy-voting and corporate governance service firm Manifest estimated Mr Diamond had earned at least £120m since joining Barclays’ board in 2005.
Mr Diamond, 60, who was with Barclays for 16 years, is expected to “speak more freely” when he appears before MPs tomorrow now he is no longer at the helm.
Meanwhile, reports claimed Bank governor Mervyn King and Financial Services Authority chairman Adair Turner last night encouraged Mr Diamond’s exit.
Mr del Missier took up his current position in June 2012 after spending three years as co-chief executive of corporate and investment banking.
In his most recent role, Mr del Missier was responsible for overseeing the construction of a ringfence around the bank’s retail arm, separating it from the investment division, as proposed by the Independent Commission on Banking last year.
Chancellor George Osborne, who announced on Monday a parliamentary probe into banking standards, said Mr Diamond made the “right decision” for the bank and for the country.
Chairman Marcus Agius, who resigned over the affair on Monday, will remain with the bank to lead the search for a new chief executive before stepping down at a later date.
Despite mounting calls for his departure, Mr Diamond’s exit came as a shock as he had showed no signs of leaving his position after pledging to see an internal review through to the end.
Mr Osborne said that a parliamentary review, led by Treasury Select Committee chairman Andrew Tyrie, will look at “transparency, conflicts of interest, culture and the professional standards” in the banking industry.
Speaking after Mr Diamond’s resignation, Mr Osborne said: “I think he has clearly taken the view that Barclays has a better future without him than with him.”