Lord Mandelson announced yesterday that the next Comprehensive Spending Review (CSR) will take place after the general election. He said that this was necessary because he did not want to make plans for public expenditure based on “speculative projections”. It is worth asking whether this was: (a) novel; (b) ironic; (c) arch; (d) reckless; or (e) all of the above. Answer: (e).

The CSR is still a relatively new instrument of government but, traditionally, it has been decided by the Treasury, not by the Business Department. Perhaps Lord Mandelson has gained such a taste for titles that he wants to add Chancellor of the Exchequer to his growing list.

His explanation for the Government’s wariness in launching another spending review could well be another instance of Lord Mandelson’s famous wit at play. After all, the idea that the Business Secretary mistrusts the “speculative projections” — otherwise known as Treasury forecasts — is darkly comic. Many critics in the City have openly questioned No 11 Downing Street’s growth projections but Alistair Darling should surely have expected the Business Secretary to respect his numbers.

There is a political rationale for the Government to hold a CSR, so it is clear why it wishes to keep the option open. Gordon Brown, as Chancellor, was usually able to time the CSR to coincide with the electoral cycle, thereby forcing the Conservatives to make plain their own spending plans at the least opportune moment. It is possible that this political logic still obtains. Perhaps the Prime Minister might calculate that, if he is going to insist on counterposing his planned investment with the cuts that he alleges are being stored up by the Conservatives, then he will see the advantage on setting out the figures.

But there is a far more reputable reason why the Government should stick to the usual timetable and announce a new review of spending. It is very simple — such a review is now more urgently needed than at any point in the span of this administration. To avoid a serious assessment of spending options, simply because the numbers are embarrassing, is a brazen and disreputable reason for inaction. At a time when the country faces borrowing £175 billion in 2010, the Government cannot ask to have any new plans taken seriously if it is so wilfully unserious about the money required to pay for them.

The credibility of the whole new Labour project rested on economic competence. All of Mr Brown’s early actions were designed to emphasise moderation and prudence. He set himself elaborate fiscal rules to exhibit just how careful he was. The CSR, which was a Gordon Brown innovation in 1997, is a good addition to the cycle of British politics. Three-year budgeting allows for better planning and clearer accounting than was possible in the annual planning cycle.

That is precisely what the country now needs. Yesterday a new reform programme, Building Britain’s Future, was published. In it, the Government has set out its twin aims of using the State to encourage enterprise in growing sectors and reforming public services by granting citizens entitlements to a given level of service, with various forms of redress if that promise is not redeemed. There is some merit in these latter ideas and it is to be hoped that the work is not wasted, whichever party wins the general election.

But the plans are worthless unless they are accompanied by credible spending plans. Building Britain’s Future comes equipped with an Incomprehensible Spending Review. The combination of a magpie manifesto with no review of spending means that the Government has no fiscal credibility. That means, in turn, that the Government’s plans look like nothing more than, well, speculative projections.