I never thought I'd hear myself say this, but good for Tesco. Britain's biggest supermarket has defied the Daily Mail's brilliant but hugely silly campaign for a ban on plastic bags. In the face of some fairly frenzied eco-bullying of all the supermarkets, Tesco's spokesman uttered a sturdy libertarian statement, declaring that Tesco's basic philosophy was to change behaviour through incentives and choice, rather than charges, taxes or legislation.

In other words, no bans. The nation's secret bag hoarders can relax. At least one organisation has reacted with common sense to the eco-bandwagon whipped up in recent days over that most ubiquitous and humble of everyday accessories.

But already the Mail's devastatingly sentimental approach has caused such a stir that the Prime Minister has joined in, giving us his own shameful bag-confessions about online shopping: “Sarah and I ...are left with a bin full of plastic bags, each bag sometimes containing just a handful of items” - Ah, the horror of it! - and he has hinted that he will consider legislation forcing all supermarkets to charge for bags.

Marks & Spencer has joined in too, putting 5p on a bag, thus conveniently diverting attention from its chronic over-packaging of food products, which must contribute significantly to the nation's landfill.

On the basis that plastic bags kill dolphins, lodge in the stomachs and beaks of wildlife, float in oceans, pollute the countryside and don't degrade, according to who you listen to, for anything from six months to 1,000 years, we must renounce them with evangelical zeal.

If you believe the polls taken to back this emotional crusade - and nothing beats a cormorant stuck in a plastic bag for emotion (except maybe a kitten, and the papers apparently couldn't find a picture of that) - you will learn that 83 per cent of people are concerned about the impact of plastic bags and 79 per cent say they would be prepared to give them up altogether.

To which the wise will sound a hearty “Aye, right”. If you want to know whether people are really prepared to give up bags, then ask why Tesco is going to continue dishing them out for free. Because Britain's most successful food retailer is a weathervane for society: it knows fine that, come the check-in queue on a Saturday morning, after a stressful family shop, people aren't going to prioritise the health of dolphins and turtles over their own convenience.

Lidl has been charging for bags for years - for different reasons - and it's one of the reasons it is not more popular with the cash-rich and time-poor. In the cutthroat world of supermarkets, free bags and a free market approach is always going to beat eco-evangelism.

And the reason people are not going to give up plastic bags? It's because they are so useful: so very, very useful, in fact, that it's hard to think of a single other household item that has more applications across every facet of our lives. Plastic bags, one might say, if it is not in too bad taste, are embedded in society to a much greater extent than they are inside a porpoise's gullet. And that is the flaw at the heart of the anti-bag campaign. You might as well try to ban glass, or fridges, bicycles or handkerchiefs; for plastic bags are just as irreplaceable. One can genuinely ask, what did we do before they were invented?

Plastic bags are symbolic of thrifty, sensible Middle England. People take for granted their phenomenal flexibility for carrying, containing, keeping water out or dampness in. Shopping is just the start of it. No man born of woman does not avail himself of a plastic bag at some point in every day, be it for carrying papers, storing smelly gym kit or wet swimming costume, protecting his lunch in the office fridge, or making a parachute for his Action Man.

And no woman, either. Among a myriad uses, plastic bags are irreplaceable for packing shoes, storing paintbrushes in, shredding for craft projects, fancy dress, keeping clothes dry in rucksacks, wrapping round plastered limbs in showers, putting wet umbrellas in, holding rubbish in cars.

We use them to protect the precious and dispose of the dirty - lifting dog waste, wrapping soiled nappies. We line dustbins and lift cat litter; we separate our recycling with them.

Besides, this is a human rights issue. What of the tramps? How can a bag man survive if there are no bags: and aren't his needs as great as the dolphins? What will happen to the frugal older generation, for whom plastic bags remain a thing of wonder, precious items to hoard in cupboards and drawers against unknown exigencies? When my parents died I found enough squirrelled-away supermarket bags to wrap the outside of the house, Christo style.

I even hear of one friend's mother, resident in France, where supermarket bags are thin and deeply unsatisfactory, who on her trips home collects a big supply of used bags to take back with her. Proving there is an inner Borrower in all of us.

Instead of banning plastic bags, we should be writing eulogies to them: the item that has changed history. Imagine how different it would have been on the Somme, for a start.

Of course we should use fewer bags. But a ban would do nothing but punish the frugal, who already deserve eco-medals, not persecution. And the even more stark truth is that there is no viable alternative. Nylon string or cotton bags aren't waterproof, baskets are too bulky, and paper bags are non-reusable and no better for the environment. So what is a bag lady to do? I think we should be told.

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