I spotted a hipster mum type strolling through Dulwich sporting the Anya Hindmarch “I’m Not A Plastic Bag” bag yesterday. In her other hand was a Sainsbury’s carrier. But then who’d besmirch her Anya’s cream canvas with leaky yoghurt and smelly old onions. Certainly not I. Not after I bought mine for a stupid sum on eBay. OK, since you insist, £80. (Plus £5 p&p.)

I know, I know. You can’t call me a name my husband hasn’t used already. “But it only cost £5 in Sainsbury,” he yelped. “Yes,” I replied. “It cost £5. But it is worth £80.” There is no starker illustration of market forces than high fashion.

And it was almost an accidental purchase. One minute – in the name of research – I was monitoring the torrent of bags onto eBay a few hours after they’d left supermarket shelves, sneering at the suckers fighting furious online auctions. The next moment I’d put in a little bid. And another . . . Then – ooh! – pop went my eBay cherry.

The bag arrived this morning and, as is the way with objects of desire, it hasn’t made me nearly as happy as I’d expected. True, it is a nifty design, well finished and the rope handles are satisfyingly chunky. But I’d had an unusual yearning for this bag because it was an elegant two-fingered salute at wastefulness and egregious consumption. Now holding this bag at last, I just felt part of the problem, soiled by blowing a silly wad on what is really non-fair-trade, unorganic cotton, stitched by low-paid Chinese workers.

Worse, I fear the scorn of my schoolyard mates. The bag’s neatly appliquéd slogan might as well read “I’m a pathetic fashion victim” or “Screwed by eBay”. Or “I queued at 4am in Sainsbury car park” which is the time 700 people descended on my local branch. The world, it seems now divides into the poor and patient, prepared to wait for hours in the dark for their heart’s desire and those who’ll pay inflated prices for someone else to do it for them, rather as rich Indians employ “queue wallahs” to stand in their stead at packed railway stations.

It is a shame for that laudable charity We Are What We Do that the bag it commissioned has now become, like Glastonbury tickets or Kate Moss’s designs for Topshop, just another consumer “must have”, at once desirable and pitifully ephemeral. Its original ecological message is diluted, since fashion leeches meaning from every cause it champions: the Peta-supporting supermodels were swathed in chinchilla and ocelot the second the fashion wind had changed.

And WAWWD is clearly on to something. A mood of nauseous disdain is growing against our disposable culture. Discarded plastic bags uglify our public spaces, clog our most far-flung beaches. But then it is a faff to remember to keep a shopper in your handbag. The jute tote stuffed in mine has, appropriately, the texture of a hair shirt. And it reminds me of my grandma who never left home without a rain-hood. So the Anya bag was a little reward for the dutiful: it ennobled and trendified our dreary, worthy little efforts. Humping potatoes up the hill, I would feel exactly like Erin O’Connor.

But alas this bag is a “limited edition” of 30,000. Its rarity value means few are likely to transport anything more than Stella sunglasses and a copy of Grazia. WAWWD and Anya Hindmarch had no idea when they first conceived the bag two years ago that it would provoke such excitement. Although once Vanity Fair chose it as the “goody bag” for its Oscars party, they probably had a clue.

You might expect that Sainsbury will already have put in a quick order for 500,000. Indeed, they gladly would and WAWWD likewise would be delighted to spread its message further across the nation that our smallest good deeds truly matter. But Anya Hindmarch refuses to manufacture more. Not for Britain at least. Another “limited edition” is planned for Japan and the US, which will no doubt provoke further high street and online scrums in Tokyo and New York – and in the uptown department stores, echoing kerchings from Anya Hindmarch tills.

When I spoke to Hindmarch’s people, they replied that the bag was only ever intended to “raise the issue”. Luxury fashion houses are predicated upon exclusivity and mystique. They fear the common herd owning their product, hence Burberry’s horror when Daniella Westbrook and her ginger baby were photographed head to toe in their beige checks.

And the Hindmarch spokeswoman added that they would take legal action against anyone making knock-offs of the nota-plastic bag. More important, it seems, to preserve the brand than the planet.

But this new limited edition culture is almost as damaging to the environment as extraneous packaging. The fashion wheel spins now at a dizzying pace. Primark and Zara get in new ranges almost daily. Clothing is disposable, unfashionable almost before it can be worn, let alone worn out. The “limited edition” bags of Gucci or Prada cost not £5 or even £80 but £800 or more, and they are sought and bought not just by WAGs but ordinary girls with more credit than sense. And next season they mortgage their futures to another mythical “must have”.

Wouldn’t if be better, if the Anya bag didn’t just raise the issue but solve the problem? What if the shelves of Sainsbury were piled high with them? Everyone owned two or three, which they took affectionately to the shops every week, replacing them when they wore out for a fiver or so. A truly democratic piece of classic design – like the espadrille, the Anglepoise, the iPod – would, more than her exquisite confections of leather and silk sold in her Chelsea boutique, bestow Anya Hindmarch with something that transcends fashion: immortality. I do hope Hugh Grant gets community service for his alleged attack on a photographer. Not because I bear him particular ill-will, but I think maybe cleaning loos à la Naomi or sweeping streets like Boy George might stir him out of his perpetual funk. Perhaps two reliable signs of a star losing his inner compass are buying baked beans in little plastic pots from posh delis and not feeling grateful that you are so admired that people wish to publish your image.

Grant should take a lesson in grace from Noel Gallagher, of Oasis, who once said: “Being famous is my job, when I leave the house, I’m clocking in.” There speaks a man who still buys his beans in tins.

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