Tory ministers have no idea if money raised from fining banks who manipulated the Libor interest rate has been spent as intended, the National Audit Office stormed yesterday.

It was revealed in 2012 that a horde of banks had been manipulating the rate — meant to represent what banks charge each other for overnight lending, but which also underpins roughly $350 trillion of financial products.

After the banks were caught out, ministers said the £688 million in fines would “go to the benefit of the public.” An additional £284m fine was later added, bringing the total to over £970m.