It's easy now to forget that George Osborne scrapped the pre-Budget report  (introduced by Gordon Brown in 1997) in the belief that major decisions on tax and spending should be reserved for the Budget itself. The new slimmed-down Autumn Statement was designed to include little more than the OBR's latest forecasts on growth, borrowing and jobs. But confronted by the failure of his economic plan, Osborne has turned it into a second Budget in all but name. His most recent statement, for instance, included a freeze in fuel duty, an increase in the personal allowance to £9,440, a cut in corporation tax, a reduction in the tax-free pension allowance and the abolition of national pay bargaining for teachers.
So it's good to see the Treasury Select Committee calling the Chancellor out on his U-turn. In its report  on the 2012 Autumn Statement, the committeee, which is chaired by Conservative MP Andew Tyrie, notes:
The OBR is required by statute to issue two economic and fiscal forecasts a year. The Chancellor’s own Autumn Statement, however, has now grown to be virtually a second Budget. There are good reasons for having a single substantial annual review of the fiscal and economic state of the country, not least to enable the subsequent presentation to Parliament of proposed tax measures and of Estimates of expenditure. The Treasury should re-establish the annual Budget as the main focus of fiscal and economic policy making.
Tyrie said: "The autumn statement is not, nor should it be, a second budget. In recent years it has come to read like one.
"The case for two budgets is weak. An additional one can create uncertainty and carries an economic cost. Only in an emergency would it be likely to carry long-term benefit. The primacy of the budget as the main focus of fiscal and economic policy making should be re-established."
OBR forecasts "biased to over-optimism"
Another concern raised by the committee is that the OBR's forecasts so far have been "biased to over-optimism". It states: "This would not be a cause for concern but for the fact that the OBR’s forecasts have implications for decisions on public policy. This is because the fiscal mandate is defined with direct reference to a forecast, and because the OBR’s is at present the only official forecast against which the fiscal mandate can be measured."
Osborne reliant on "uncertain" 4G and Swiss tax windfalls
MPs also criticise Osborne for placing so much reliance on the anticipated windfall from the sale of the 4G mobile spectrum and Swiss tax repatriation to meet his borrowing forecasts.
The sums expected from the sale of the 4G spectrum and Swiss tax repatriation represent the majority of the additional receipts the Treasury intends to offset against the tax reductions and investment announced in the Autumn Statement for 2012–13 and 2013–14. Both are subject to uncertainty. In the case of the tax repatriation from Switzerland, the proceeds may not meet expectations if assumptions about the potential tax liabilities and expected behaviour of those affected prove not to be valid.