He said the Treasury had given an undertaking for £3.5m for the 2012/2013 financial year, and the same amount for each of the next two years, should the SFO need to use it.
Asked if this was a good use of taxpayers’ money, the spokesman said: “This is just an undertaking and will only be used if it is not covered in our own budget. You have to have some suspicion to commence an investigation. We will always manage money carefully.”
The spokesman added that SFO’s budget for this year was £31m.
The announcement comes after shadow attorney general Emily Thornberry submitted a parliamentary question on what extra funds the SFO had requested.
A response from Oliver Heald, solicitor general, said: “The SFO has asked for additional funding for one current investigation relating to Libor.”
The SFO launched a criminal investigation into Libor fixing last year after the FSA began fining banks for their role in manipulation of the rate benchmark.In December three men, aged 33, 41 and 47, were arrested.
Andrew Whiteley, managing director of Hertfordshire-based chartered financial planner Provisio, said: “Whatever the SFO has to spend it will have to be confident it can recoup in terms of fines and it will need to produce a thoroughly detailed dossier showing the likely outcome for fine revenue.
“However it seems counter-intuititve to support the banks with taxpayers’ money and then take it off them through fines. The whole Libor investigation seems to be a bit of a witch-hunt and I can’t see the end result benefiting anyone except the Exchequer.”