The US Federal Reserve raised concerns about LIBOR as early as 2007 and shared proposals for reform with the UK regulator, according to reports.
Reuters reports that the Fed first noticed there was an issue with LIBOR setting in August 2007, and that it conducted enquiries with Barclays in 2008.
A Federal Reserve statement read: "in the context of our market monitoring following the onset of the financial crisis in late 2007, involving thousands of calls and emails with market participants over a period of many months, we received occasional anecdotal reports from Barclays of problems with LIBOR.
"In the spring of 2008, following the failure of Bear Stearns and shortly before the first media report on the subject, we made further inquiry of Barclays as to how LIBOR submissions were being conducted.
"We subsequently shared our analysis and suggestions for reform of LIBOR with the relevant authorities in the UK."
Last week former Barclays chief executive Bob Diamond told the Treasury Select Committee he had been unaware of any issue with LIBOR until this month.
Yesterday the Bank of England’s Paul Tucker appeared before MPs to deny he had encouraged banks to manipulate LIBOR, under pressure from Whitehall.
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