George Osborne, shadow chancellor, has today given a keynote speech to the Conservative Party conference, promising “honest choices” over the deficit and risking public intolerance of specific spending cuts.

Using the end of the next Parliament as a reference point, the Conservatives claim they have found £7,000m of spending cuts a year. Assuming all of this is in addition to the government’s deficit reduction plan, this would cut the projected deficit in 2013-14 from £97,000m to £90,000m. That represents a reduction in the projected deficit by 0.4 per cent of national income to a deficit of 5.1 per cent of GDP.

The important point is that on the most generous assumption possible to the Conservatives, the additional deficit reduction hardly matches Mr Osborne’s promise to “tackle [the budget deficit] decisively if we are to stop high interest rates and the unemployment they bring”. It is less than one year of average forecasting error in the public finances.