Do you remember that unspeakably naff designer accessory, I'm Not A Plastic Bag? The "design", by Anya Hindmarch, involved thinking up the gauchest slogan ever contrived then printing it on a white shopping bag of the kind old ladies used in the 1960s. Tens of thousands were sold, at mind-boggling prices.

More to the point, does anyone still use one? There still seems to be a small market among collectors – there's one for sale on eBay at the moment for £179.99 – but when did you last see someone shopping with one? This excrescence was supposed to be the antidote to the throwaway society. Perhaps the bags haven't been thrown away, but no self-respecting celeb would be seen dead with one now. They are sooo last year. Anya Hindmarch doesn't sell them any more: now she markets a new range of granny bags (starting at £165), printed with glossy pictures of designer children, dogs and motorbikes.

As Oscar Wilde said: "Nothing is so dangerous as being too modern; one is apt to grow old-fashioned quite suddenly." These bags for life were discarded with all the other eco-bling as soon as something newer came along. But they served their purpose: they permitted the rich and famous to telegraph their green credentials while still running the Aga, the Range Rover, the yacht and the second and third homes in far-flung parts of the world. By buying the bag, they could tick another box: now, among their other attributes, they were environmentally conscious.

I was reminded of this when I saw the British government's new green initiative, the "Get a bag habit" campaign to encourage reuse of bags, which it launched yesterday with the British Retail Consortium. Not just because the slogan almost rivals Hindmarch's for naffness, but also because it highlights our fetishisation of the plastic bag as the root of all environmental evil.

Don't get me wrong – I don't like plastic bags either. We use too many of them, just as we use too many of all the earth's resources. They litter the countryside and cause problems for wildlife when they end up in the sea. But their total impact is microscopic by comparison to almost anything else we do. As environment writer George Marshall records in his excellent book Carbon Detox, our annual average consumption of bags produces 5kg of carbon dioxide a year. Total average emissions are 12,500kg.

Plastic bags aren't even a very large component of domestic waste. Plastics in general – according to a study by South Gloucestershire district council – account for 18% of total household waste. Plastic bags account for 18% of the plastic, which means 3.2% of total waste. Clingfilm (23% of domestic plastic waste) produces a greater proportion than plastic bags.

The British Retail Consortium, in helping to launch this campaign, says that "this is a symbolic step towards using resources more wisely." It's a symbolic step, but not a significant one. By no stretch of the imagination does it justify the hype it generates. We could eliminate every bag in the UK and make only the tiniest dent in our total environmental impact.

So why this fetishisation? Because dealing with plastic bags is easy. Easy for the government, easy for retailers, easy for shoppers. It threatens no one, makes money for the shops (if they charge for their bags) and ensures that everyone feels better about themselves, while continuing to trash the biosphere just as we did before.

Monbiot.com