IMAGINE a world in which, once a week, a box of organic vegetables is delivered to your door; staples like eggs and cheese come from small, independent shops where you are greeted like an old friend and the remainder of your fresh food comes from farmers' markets. Imagine - if you can - only setting foot in a supermarket about once a month, and even then, only buying non-food items like detergents and toilet roll.

Chances are, this shopping routine is far removed from your own and those of everyone you know. It sounds like that of someone with a lot of time on their hands - someone, in effect, who could never be you. Yet it's how mother and professional food writer Joanna Blythman stocks up on the things she needs, and what's more, she believes it's neither less convenient, nor more time consuming, than the conventional weekly supermarket sweep.

In her latest book, Shopped: The Shocking Power of British Supermarkets, Blythman outlines her shopping philosophy and explains why it's dangerous to allow supermarkets to continue in their quest to control the entire retail market. She warns that far from playing a benign role in our everyday lives, they are strangling choice and seeking to manipulate us in ways we may not even be aware of.

For example, how many of us have thanked our lucky stars for the supermarket ready meal? Just a few minutes in the microwave and, ping, mealtime problem solved. What could be easier or more convenient? Yet Blythman points out that while the British spend a staggering £7,000 on ready meals every minute, we are hardly getting value - or, for that matter, nutrition - for money. She says that one chef who tested a selection of Marks & Spencer ready meals estimated that its £1.99 vegetable and pasta bake would only cost 40p to make at home, while a £5.58 beef casserole would cost £1.50 if home made.

Blythman is also scathing in her criticism of the quality of ingredients used by supermarkets. She points out that the same companies often supply different chains with generic sauces, so that one Thai green curry tastes very much like another, and a "tomato goo" pizza topping can be adapted as pasta sauce. Audaciously, supermarkets will even dream up completely erroneous descriptions to make food sound more enticing, such as Sainsbury's American-style mini battered chicken fillets, which she says have nothing discernibly American about them.

More worryingly, Blythman suggests that false claims by supermarkets that their meals are healthy could be contributing to Britons having the worst diet in Europe. She cites the examples of Asda's 'Good For You' lasagne, found to contain 60 per cent of an adult's daily recommended salt intake, and its korma with rice in the same range, containing 55 per cent. Even children's meals ranges like Sainsbury's Blue Parrot Caf and Safeway's 'I'd like' have to be qualified by the word 'healthier' and are, says Blythman, "in reality, nothing more than slightly improved versions of the usual lines".

An obvious consequence of supermarkets' rise is the decline of small, independent retailers offering genuine choice. In his book, Sold Out: the true cost of supermarket shopping, Dr William Young, an environment, sustainable development and business lecturer at Leeds University, estimates that every time a large supermarket opens, 276 jobs - mostly from small shops - are lost. He refers to findings by the social think tank The New Economics Foundation which resulted in a report called Ghost Town Britain. The report shows that while we used to be a nation of shopkeepers, we are now one of shop-busters. Between 1995 and 2000, we lost roughly one fifth of our local shops and services, and if current trends continue, we will lose one third of what is left over the next ten years. This is not just in villages and market towns, but also in urban and suburban areas.

Blythman, who lives in Edinburgh, admits she's lucky to have a network of good, independent shops close at hand. She says she wrote the book after spending four years living in France, where shopping in small stores is very much the norm. "I learned a completely different kind of shopping. It was such a positive, life-enhancing experience to shop for food," she says. "When I came back to Britain, the thought of going back to supermarkets was just so depressing. It was a Stepford Wives-type experience."

In The Atlas of Food, Erik Millstone and Tim Lang highlight the environmental impact of world food trade dictated by supermarkets. To meet the demand for year-round fresh fruit and vegetables, more and more food is being transported by air. This facilitates a permanent 'dietary summer' in which strawberries can be bought in November, but is costly in energy and environmental damage. A single family's weekly vegetable purchase, for example, will often have travelled a distance equivalent to several journeys round the equator. The unnecessary importing and exporting of food also increases the spread of problems like foot-and-mouth disease and as affluent countries financially support their own producers, those in poorer countries suffer. While we in the West are obese, those in developing countries are starving.

Both Blythman and Young believe a combination of Government and consumer action is necessary to halt supermarkets' worrying ascent. Young urges people to stop expecting fruit and vegetables to look 'supermarket perfect', buy Fairtrade, Marine Stewardship Council or RSPCA products and ask their local supermarket to stock local, regional and UK products. He calls for the Government to introduce grants and tax breaks for locally-produced and Fairtrade foods, tax plastic carrier bags and force supermarkets to evaluate and display their environmental and ethical trading policies. Blythman suggests legislation to cap the size of all new supermarkets, appoint a supermarket regulator and reduce rates for independent food retailers.

When it comes to what the individual can and should do, she quotes the Tesco slogan: "Every little helps". While she doesn't object to supermarkets per se - she would be quite happy to see more "moderate-sized, well-stocked" stores, like the North-West's Booths - she urges people to help counteract their "neutron bomb" effect by exploring the alternatives. She says: "Even if people moved five per cent of their average supermarket shop to independent retailers it would make a massive difference. I think we need to wake up to what's going on."

l Shopped: The Shocking Power of British Supermarkets by Joanna Blythman (Fourth Estate, £12.99); Sold Out: the true cost of supermarket shopping by William Young (Vision, £10.99); The Atlas of Food by Erik Millstone and Tim Lang (Earthscan, £12.99)