Building more is not the easy answer. If it was, we'd have done it already

With each new growth-friendly infrastructure project comes a thousand caveats

The HS2 project is bitterly opposed by some MPs

I’m not saying infrastructure is a bad idea, exactly, but if it really were the answer to all our problems with the economy, wouldn’t we have built it by now? Plus it leads politicians into temptation and to trespass upon cliché, as they get all gooey about shovel-ready projects and groundbreaking initiatives.

Not only that, but it is a horribly unspecific, latinate word. Under-structure. Why don’t we just call it that, then everyone would know what we mean? That is, a high-speed railway in a deep tunnel all the way from the new underground London airport to Scotland. Putting everything underground would solve an awful lot of planning problems, come to think of it. We could have hobbit-houses all over the formerly “environmentally uninteresting” fields of oilseed rape that would now be interesting because they would be all bumpy.

So let us say what we mean and realise that we are not so much in favour of it as we thought we were. Infrastructure means airports. You know, that third runway at Heathrow that the Conservatives and Liberal Democrats said, in their manifestos, that they were against, and which Labour was in favour of, in government, before it was against, in opposition. There is a reason that all three parties are against it, which is that it is a bad idea.

Air travel is one of the fastest-growing sources of global warming gases. A developed country such as the UK has to draw the line somewhere and say we don’t need any more airport capacity, that we should use what we have more efficiently. Fortunately, Heathrow expansion is never going to happen, for the simple fact that 30 per cent of people in the entire European Union already affected by airport noise live near Heathrow. Boris Island is a wildly expensive, locally ungreen scheme, that will also never happen, or so we can hope.

Infrastructure means roads. We have been round this roundabout already. We know now that building roads creates more traffic. Planning law rightly makes it harder and harder to build them anyway, forcing us, as with air travel, to use the existing network more efficiently.

Infrastructure means railways. Good. We like railways. They are green and more middle-class than roads. Lots of little railways, please. But instead we are being offered HS2, a monster project, already vastly over budget with not a single compulsory land purchase even in the courts. A monster project being driven right through the one part of the country where planning permission is most difficult: west of the A1/M1 and south of Corby. The South Province of England where everyone is BANANAs, as David Cameron once said: “Build Absolutely Nothing Anywhere Near Anyone.”

Which brings us to houses. Everyone agrees that building more houses is the solution to rising house prices, which are pricing a whole generation out of home ownership. But no one wants the new houses anywhere near them. It’s enough to make you feel a twinge of sympathy for Nick Boles, the bright, modernising Tory Planning Minister.

And I haven’t mentioned shale gas and nuclear power stations. For every job-creating, growth-friendly “infrastructure project” there are a thousand caveats in the specifics.

So, when George Osborne announced some big numbers for infrastructure spending this week, it sounded good. But now that Danny Alexander has announced the list of projects, we should think again.

John Rentoul is chief political commentator for The Independent on Sunday