Alistair Darling has accused the Conservatives of not carrying out sufficient research when making their calculations on cutting waste this year. Highlighting comments from Standard Life Chairman Gerry Grimstone, Mr Darling said:

"It is not credible because of their £12 billion additional savings, most are already being delivered, counted and banked and you cannot spend money twice."

The Chancellor criticised David Cameron for being overly optimistic and indulging in "reckless opportunism" with their aims to save an additional £12 billion on top of Labour's planned £15 billion savings.

Darling said that the figure could not "realistically be delivered in 2010-11, particularly three months into the financial year", and he told the public to ask themselves if they really want "to gamble your economic future on the basis of a back-of-envelope set of calculations like this?"

The Conservatives are claiming to be able to save a total of £27 billion which is the equivalent of half the education budget.