In this time of national adversity the country needs leadership by example. Instead of fan-mailing X Factor finalists, Gordon Brown should be down in the Westfield shopping mecca rewarding Sarah for swinging that Scottish by-election with a Christmas splurge in Jimmy Choo. Why are Tessa Jowell and Jacqui Smith not tripping into Cabinet, ministerial wrists buckling under Accessorize bags? We need to see Lord Mandelson test-driving sporty runabouts, Alistair Darling running amok in PC World.

If, truly, spending our way out of a recession works, if the Government believes bunging us a 2.5 per cent off VAT shopping voucher (Hurry! Offer lasts only 13 months!) will kickstart the sputtering economy, we need evidence of their own personal consumer confidence. Because do you have any? I sure as hell don't. And by the look of this week's Populus poll, four fifths of us will take the Chancellor's bit of fiscal stimulus and either squirrel it away or pay off our already maxed-out cards. Only 18 per cent say they will rise to their patriotic duty and shop.

Never has government strategy been so counter-intuitive: just as Robert Peston's voice reaches a new pitch of hysteria about lay-offs and receiverships, we are being relied upon to unleash our wallets. And now Britons are hit by the Woolworths Effect: if we can lose our Proustian Pick'n'Mix, is anything safe any more? Suddenly the credit crunch is no longer a remote and dreary theoretical horror - like global warming - but a tsunami chasing us, screaming, down the high street.

Oxford Street this Christmas has never looked so tawdry. There is a pitiful desperation to the “40 per cent off” signs in Monsoon; the animatronic shop-window Santas seem like show-must-go-on old hoofers; and spangled party frocks hang in Jane Norman, vestiges of a cheerier age.

In Westfield, West London's humongous new mall, I see many browsing but few carrying bags. I try on a red top in Gap which I like but don't buy. A purchase now involves a chain of calculations where previously it was a one-click act. In good times you buy because you feel depressed, frivolous, deserving, defiant, dowdy, bored. Now the decision is down, mostly, to need. And I already have several red tops.

Not that I couldn't afford a lovely new one. It is just, for the middle classes, that shopping carelessly has lost all appeal. A friend with multimillionaire clients says they have all cancelled their customary Christmas holidays. Sure, they could afford Tobago as usual, but this year it just doesn't feel right. Likewise friends with solid jobs and plenty put by are glaring at their utility bills, swapping Taste the Difference for Basic Range and downscaling their children's Christmas hopes.

So who then is willing to help out the Chancellor? I would bet that the 18 per cent of shop-hards is made up principally of the young and the poor. The under-30s entered adulthood with college loans and are thus undaunted by debt. Moreover the very architecture of their lives - coffee bars, internet cafés, boutique hotels - bespeaks an ever-prosperous, upward-moving world. They were told things can only get better, never worse. They are following a biological urge to preen, dress up, meet and mate.

Besides, nothing they own is meant to last: clothes are disposable, technology instantly obsolete, fashions pass in a blink. They will be the last to comprehend that recession is not a trend - a wave of austerity chic after a decade of fin de siècle decadence - but a real and unstoppable force, which will clip their easyJet wings and turn arsey, entitled, A-starred graduates into a listless and prospect-free new Generation X.

For the poor, who have little to lose, the future has never been something you could plan for, so why begin now? If Mr Darling knocks a ton off their plasma telly, verily they will go unto Dixons once more.

So upon the debts of the desperate, the future mortgage deposits of the young, the rash spending of the feckless, the economy will feed, and revive. Meanwhile, it is suddenly apparent how green politics are a luxury we ditch like posh biscuits in times of need: celebrate the drop in petrol prices, get the country driving to the malls, stretch that carbon footprint, increase the capacity of Heathrow whatever the cost in noise or pollution. Sod sustainability for short-term gain. Anything to reinflate that punctured credit bubble.

Has capitalism ever looked so absurd? In boom years, with ingenious new enterprises fanning out across the globe to anticipate and fulfil undreamt-of needs and desires, capitalism was like the dazzling all-knowing computer in Minority Report. Now capitalism looks like a “penny pusher” arcade game: if you roll in a coin, the layer of coins beneath will shift and maybe - just maybe - if you shove in enough, you are deluged with pennies. Beside the machine stands Mr Brown begging us to empty our pockets, to have faith and cough up one last coin.

But who trusts the gamble? Who is willing to put the nation's economic interests before our own personal finances? Those quietly enjoying thrift's less drudgey practices - reading library books, growing lettuce in window boxes, vintage clothing, making soup from scraps - congratulate ourselves on our virtue. But maybe if you hadn't re-covered that old sofa, 3,000 jobs could have been saved at MFI. Frugality, make-do-and-mend, sitting on savings will send the economy spiralling down from recession to depression. Don't you know every time you shut your purse, a call-centre worker's baby cries?

Although not all agree with this diagnosis. Not Barack Obama, who made a mockery of George Bush's post-9/11 declaration that the American people should defy terrorism by going shopping. He said recently: “We will all need to tighten our belts, we will all need to sacrifice... because now more than ever, we are all in this together” - a call for collective forbearance and austerity that is very old Labour indeed. Who cannot feel uneasy that Darling's 2.5 per cent discount voucher is being pillaged from next year's hospital and school budgets or will simply be billed to us in taxes?

Today happens to be Buy Nothing Day, an idea that began in America as a 24-hour holiday from consumerism, which feels this year like an odd form of sedition. So, Gordon, will you lead us in a collective shopathon? Can we expect you down Bluewater this afternoon with your patriotic plastic, ready to forsake Presbyterian parsimony for the national good?

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