Republicans, by contrast, will argue that allowing the payroll levy to expire is not a tax increase at all since it was always scheduled to come to an end.

FORBES: Obama And Boehner Set To Swap Roles In Payroll Tax Fight

More pertinently, an increase in the tax rate will hit the big British banks hardest, because - unlike their overseas rivals - the levy applies to all their borrowings, on a worldwide basis, not just their UK borrowings.

BBC: Autumn Statement: Bankers hit by third levy increase