The first budget of a Parliament is often the one the Chancellor who introduces it is best remembered for.  Geoffrey Howe doubled VAT in 1979 – part of a shift from direct to indirect taxation that marked the Thatcher years.  Gordon Brown raided pension funds for tax in 1997, a giant step in the story of the collapse of Britain’s private pension system.  Nigel Lawson cut income tax and corporation tax in 1987 – though the budget he is most associated with is probably the one of the following year, in which he slashed the top rate of the former back to 40p.

In order to make these opening budgets effective, three conditions must usually be fulfilled.  First, the Government in question must enjoy a Commons majority sufficient to get its measures through.  Second, the Chancellor must be as selfless as a politician possibly can be.  That’s to say, he must put the Government’s welfare ahead of his own ambitions.  Third, he must have a clear plan, regardless of any merit it may contain.

All three of these conditions applied to George Osborne in 2010.  The Coalition may have been fractious, as David Laws’s memoirs are reminding us, but it had a majority of roughly 80.  David Cameron was in place as Prime Minister, evidently intent upon winning a majority of his own if he could in 2015, and Osborne was supporting him unequivocally and unselfishly in what remains the most enduring political partnership of modern times.  Finally, the Chancellor had an objective: to get down a deficit that threatened to become the biggest in Europe.

This time round, for the first Budget proper of the first majority Conservative Government for over 20 years, none of these conditions clearly apply.  Cameron won a slender majority of 12 last May.  He has announced that he will not seek a third term as Prime Minister, thus effectively firing the starting pistol of the leadership contest to come.  And that Osborne seeks to be a contestant in it has weakened his effectiveness as Chancellor.

Consider his Autumn Statement of last year – the forerunner of the budget he will present on Wednesday.  A central fact of Britain’s economy, for all Osborne’s success in helping to create growth and jobs, is the size of the deficit – not eliminated, the aim to which the Conservative Manifesto of 2010 aspired, but (on one measure) approximately halved.  The Chancellor could have presented a sober statement concentrated on further deficit reduction.  Instead, he played the showman – lauding the improved forecasts that handed him extra cash to meet his welfare and surplus targets.

However, the walls were closing in on him even as he presented his statement.  It contained the abandonment of his plan to find savings from tax credits – forced on him not only by a vote in the Lords but by a growing revolt against it from Tory MPs in the Commons.  Since then, the deadly combination of the fragility of the Government’s majority and his own leadership aspirations have scuppered plans for the reform of Britain’s flawed pension settlement.

The Budget is thus unlikely to contain radical plans for structural reform – the simplification of the tax system, say, which was such a preoccupation of Lawson’s in his time as Chancellor.  Furthermore, the forecasts are likely to turn sour for Osborne.  Having rushed out last autumn to declare that the OBR had found him some extra cash, he confirmed yesterday that he will rush back on Wednesday to announce that it has downgraded his forecasts, and that he must now find new savings to meet the surplus target that he himself introduced.

Only his leadership ambitions – or white noise from the Treasury or elsewhere in Government – can explain why, in this grisly context, stories are appearing in the papers, including today’s, of taking more people out of tax and raising the threshold of the 40p rate.  This is not the time in the political cycle for income tax cuts unless they march in step with very deep reductions indeed in the rate of spending increase.  Better to save them up for nearer 2020.

But it is not only the Government’s lack of a workable majority – at least given the propensity of Conservative MPs to rebel – and Osborne’s ambitions that threaten to undermine the Budget.  June’s EU referendum is looming into view.  It is hard not to see any income tax cuts as sweeteners for the vote (with the exception of any cut in the 45p band, which would make economic sense but be politically toxic).  The Chancellor seems still to hanker after the restructuring of the top rate that the Liberal Democrats denied him.

What then should he do?  A prelimary point to make is that gloomy prognostications from Osborne about the fragile state of the world economy cut both ways.  He will argue that this is no time in which to leave the EU – to which the obvious rejoinder is that, if the Union is in such a blighted condition, why would we want to stay?  The fate of Angela Merkel’s CDU in Germany’s regional elections is a grim political indicator.

All in all, the Chancellor should seek to take three actions that are united by a common theme.  The first is that he should keep going on deficit reduction.  I do not want to give the impression that, simply because he found some new money from projected growth last autumn, Osborne is not getting tough with the spending departments.  Peter Hoskin has demonstrated many times on this site that although the Chancellor has not realised his deficit reduction ambitions he has delivered the reductions he promised, squeezing the DEL totals tight.

The second, as Peter argued yesterday, is to protect infrastructure spending.  He needs to do so now and will need to in the future too, especially if a downturn comes sooner rather than later.  Having first taken Alistair Darling’s planned cuts in capital spending into his plan, during the last Parliament, he later changed course and began to ramp capital spending up again.  This was right and should continue.

Finally, there is the One Nation element.  Any cuts in taxes for better-off voters must be balanced by the richest ones paying more.  There are ways of plucking feathers from the geese that would have minimal impact on jobs – such as one we have previously suggested: raising property taxes in the south-east on the most expensive properties, maybe through a new council tax band.  And, needless to say, we recommend the garden cities and neighbourhood planning approach set out in the ConservativeHome Manifesto for housing – perhaps the most glaring social justice issue today.

And that common theme?  It would be for Osborne to set aside the temptation to smooth the path to June’s referendum, or seek to curry favour with Conservative backbenchers through income tax handouts, and present a dull, deliberate, purposeful Budget with no purpose other than to fix that fabled roof while the sun is still, if not exactly shining out, clearly visible.  The Chancellor who likes to pull surprises instead should dare to be dull.