It has been nice this week to hear some human-scale figures being bandied about by politicians, rather than the unfathomable billions and trillions we have lately become accustomed to. Cumbria county council pledged £50,000 towards the relief effort, after the devastating Lake District floods. Gordon Brown promised £1m towards clean-up costs. Hilary Benn, the environment secretary, has taken the opportunity to point out that without the £40m ploughed into flood-risk management in Carlisle after 2005's 1,000-year deluge, things could have been a lot worse. And the Association of British Insurers has suggested that claims for the damage will be between £50m and £100m.

Yes, it has been nice, all this talk of mere tens of thousands, mere millions. But it has been a little bit unrealistic. So far, 16 bridges have been closed or destroyed in Cumbria, taking other utilities – electricity, phone lines – with them. A total of 1,600 bridges are now being inspected, to see if they too are less solid that they seemed a week ago. One entire community has been all but marooned, and a temporary railway station has been erected, to help with sudden demand for the local rail service. The cost of replacing lost infrastructure will not be a mere bagatelle. And no one is arguing with the idea that the government will have to find the money, not even those blue-eyed boys who like nothing more than to profess their hatred for the "big state".

On the contrary, the Confederation of British Industry, at its conference this week, insisted that more transport infrastructure, along with more broadband investment and new nuclear power, should be items at the top of any government shopping list. I have no argument with that, and I don't think John Maynard Keynes would either. It is just the sort of spending he had in mind when he exhorted governments to throw money at recessions, racking up deficits on their way if they had to, in order to get the economy growing again. Actually, it's just the sort of thing that many governments spend money on, even when they are not in recession. The destruction in Cumbria, however, is a horribly timely reminder that successive governments of the late 20th century in Britain have not done this.

Early on in the financial crisis there was a lot of discussion about how high public spending should be allowed to go, as a proportion of gross domestic product. Plenty of people say there is no need to be anything other than relaxed about current spending, which is inching towards 60%, since it is historically that high in some other European countries. Actually, Britain spends more relative to GDP than the European average. But other European countries do spend more. In Sweden, government spending was in recent years higher than ours at around 57% of GDP. Likewise in France, 55% is accepted and managed.

Except that these governments have spent money on physical infrastructure, while the outcomes of the money they invest in health and education are widely perceived as better than in the UK. In Britain, the harsh fact is that public sector productivity has actually fallen since 1997. Sadly, our inroads into future clean energy provision, or smarter, faster rail services, have not been impressive either. (Although there are signs that the long slumber on both might come to an end.)

Anyway, focus has moved from spending to deficit. Britain's is increasing at a rate of £3bn a week. Government projections put the deficit at £175bn in 2009/10, or 12.6% of GDP, though others suggest it will be more like £200bn, or 18% of GDP. Compare that with Sweden or France and things are not looking rosy. Sweden's projected deficit is already down to 3%, while France's is projected at 8.5%, which before the financial crash would have been considered dangerously high. Yet even if the fiscal responsibility bill, undertaking to half the deficit in four years, were a magic wand, we'd still be spending a lot of money, now and in the future, on servicing debt, not building bridges, or railways or power stations.

That's why both the government and the opposition are only half-right as they wrestle in their phoney fight about public spending. Of course it would be idiotic to cut public spending in the middle of a recession. But it would not be idiotic to redirect it. The great trouble is that the government is pouring money into stuff that is not laying the groundwork for the sustainable economy that everyone wants for the future.

Instead, they are throwing good money after bad, into social services that leave many people feeling they have not been socially served. Oh, and banks. Sure, banks are necessary infrastructure, just as bridges are. But the money that has been spent on shoring up the banks is like money spent on shoring up condemned bridges. They may still be there. But they are useless because they cannot bear any weight. Post-stimulus borrowing levels in the private sector will build neither bridges nor much else.

Anyway, the presupposition that such things as tax rises and public spending cuts can wait until the economy picks up is based on the assumption that somehow economic growth is one day soon going to be as strong as it was before the crash. How? Asset prices may be on their way up again at the moment, but you'd have to be a rock not to have noticed that it was an asset price bubble that created the boom and the bust in the first place. Who wants that again? It's a sign that the investment economy remains glibly short-termist.

What if some mad, unsustainable consumer boom was reborn, temporarily? Would it offer a breathing space? Even before the crash public spending was outstripping revenues. The Institute for Fiscal Studies warns that the present deficit is largely structural rather than cyclical and predicts a structural deficit of £140bn. Even if this turns out to be exaggerated, it is surely clear that tax rises and spending cuts and infrastructural investment are unavoidable. Yet hardly a soul seems willing to accept this surely obvious conclusion.

The Hastings Bonfire night, like all the Sussex Bonfire society events, places the big, bad guy of the year on the big, bad fire of the year. This autumn it was "Bankers, Politicians, and NHS Parking". The first two one can understand. But the third? I'm afraid public anger over paying to place one's car in a hospital car park, instead of finding a free space 400 yards away and walking, or taking public transport, is indicative of what an unrealistic bunch we have become.

Sure, we can dump Trident, we can dump ID cards, we can withdraw from Afghanistan, we can raise property taxes. But issues far more fundamental even than these must be grasped. Far from interpreting "free at the point of access" as meaning "no parking costs for visitors", we are going to have to accept that even the nasty Tories, with their promises to guard the NHS with their lives, are being overly utopian. It is time for us to understand that if we want a sustainable and secure future, then everything has to be reassessed, and much will have to change. Otherwise, our taxes will be spent on servicing debt until all of our bridges are swept away, and there is no way back.