Top Bank of England officials were told about Libor rate rigging as early as 2005, witnesses claim.
Court documents unearthed by the Mail reveal that fears were raised about the toxic rate years before the financial crisis.
And they cast fresh doubt on evidence given to Parliament by ex-Governor Lord Mervyn King, when he denied all knowledge of wrongdoing.
The Bank of England has always denied any role in the scandal
A fresh review of thousands of Libor documents reveals that regulators secretly discussed the rates at least four times before Lord King told MPs that a trawl of records revealed ‘no evidence of wrongdoing or reporting of wrongdoing to the Bank’.
It follows a BBC Panorama investigation which uncovered a secret recording in October 2008 of Barclays staff discussing how the Bank of England had asked them to fix rates to give a false impression of the lender’s financial health.
Fraud investigators are now probing claims the Bank of England ordered lenders to change their rates at the height of the financial crisis, making them look stronger than they really were.
It follows the conviction of a string of traders who rigged Libor – which is used by banks to set their borrowing costs – to boost their profits.
But while Lord King and colleagues now have lucrative jobs in academia and the private sector, they are languishing in jail.
The Bank of England has always denied any role in the scandal – insisting it knew nothing of any criminality and never attempted to fix rates itself.
Doubts: Ex-Governor Lord Mervyn King has denied all knowledge of wrongdoing.
Last night, its former Governor told the Mail that he stood by his original comments made to MPs back in July 2012.
He said: ‘There is a world of difference between dysfunctional markets and criminal behaviour designed to profit individual traders.
This difference was examined in detail in the Treasury Committee.
My evidence was clear and I stand by it. Any suggestion to the contrary is completely untrue.’
A Bank of England spokesman declined to comment.