The Chancellor has to deliver a watertight Budget

George Osborne is preparing to deliver his Budget Photo: Press Association

Predicting what will be delivered in a Budget speech is not an exact science, to say the least.

But there is one thing we can predict about George Osborne's speech today: he has very little room for manoeuvre.

There is no money. Tax receipts are flat. And borrowing has been heading in the wrong direction for much of this last financial year (up rather than down).

So while you can expect a further delay in fuel duty, and another rise in the tax free allowance to the £10,000 target (which to be fair is a huge gain for most low earners) this Budget will be very much "steady as she goes."

The last Budget delivered at the House of Commons dispatch box went - to put it mildly - a little off course.

George Osborne delivering his Budget statement to the House of Commons last year. Credit: PA

In fact, if he delivered something similar this year, I doubt George Osborne will see it through to the next election.

Poor decisions, bad execution, wrong messages and tax reforms which, as we now know, quickly unravelled around ministers' necks.

From Tuesday's Cabinet announcement on spending (get the bad news out of the way for something good) we know there is an effort to shift resource, or day-to- day, spending to capital spending.

At the Cabinet table George Osborne and his Liberal Democrat Chief Secretary, Danny Alexander, ordered colleagues to find an additional 1 per cent in savings from their departmental budgets for each of the next two years.

That is in addition to the cuts already demanded (1% in 2013/14 and 2% in 2014/15).

The "efficiencies" will raise £2.5 billion. So bad news done Mr Osborne will, on Wednesday, say how he is going to spend it.

Much of the capital spending will be allocated to a huge house-building programme as well as other infrastructure projects.

The house-building industry will benefit from capital spending Credit: PA

The construction industry, which has recently depressed the GDP figures, will no doubt be very pleased.

But with the UK teetering on the edge of a triple dip recession, the Chancellor will almost certainly have to downgrade his growth forecasts yet again.

And the disappointing (and consistently lower-than-predicted) GDP numbers will mean Mr Osborne is likely to further delay his debt target (getting the debt-to-GDP ratio falling) by another year.

No Chancellor can appease all his critics (and George Osborne's now include those inside his own party).

But he does have to deliver a watertight Budget.

One that satisfies those who lend us money and set our interest rates.

And one that keeps dissent at bay on the Conservative backbenches.

It's a Budget for David Cameron's political future as much as it s for George Osborne's.