Mervyn King, the governor of the Bank of England, told Barclays Marcus Agius on 2 July that Bob Diamond had lost the support of the regulator.
Despite having no official power over the bank, King took the extraordinary step of intervening directly in the wake of the LIBOR scandal to ensure Diamond was removed, it has been revealed.
Speaking at a Treasury Select Committee hearing, Barclays chairman Marcus Agius said the governor spoke to Agius and non-executive director Sir Michael Rake the day before Diamond resigned.
Agius said: "It was made plan to us Bob Diamond no longer enjoyed the support of his regulators."
Agius and Rake then contacted the FSA before calling Diamond himself.
"We explained what had happened. He (Diamond) was not in a good place," said Agius.
On Tuesday (3 July) Diamond resigned as chief executive of the bank, a role he had held since 2010.
Agius - who himself handed in his notice on 2 July before reversing that decision once Diamond went - said prior to the weekend shareholders still supported Diamond and wanted him to stay on, despite the £290m fine from US and UK regulators for manipulating LIBOR.
"The message we received from the market was that one outcome shareholders did not want to see was Bob Diamond exiting," he said.
However, following the conversation with King, Agius and Rake were left in no doubt as to what needed to happen, with Diamond then resigning.
Agius earlier said Diamond will give up the £20m in deferred bonuses owed to him by the bank. The chairman said Diamond's total payoff will be £2m in total, made up of 12 months' pay and cash payment in lieu of a pension.
Six hours for a client report
700,000 transfers in 12 months
104 delegates attended
'Benefit from healthy cash levels'
Could be two months to complete payment