The Big Question: Are supermarkets changing our way of life, and should we be alarmed?

Why are we asking this question now?

Campaign groups are protesting at the "corrosive" impact the big grocers have on everyday life and demanding new limits on their businesses, from tighter planning laws to a new consumer watchdog. Hugh Fearnley-Whittingstall, the television chef behind the River Cottage enterprise, is fronting the campaign.

Who doesn't like the supermarkets?

There are many opponents of the supermarkets, which take 72 per cent of the £76bn spent annually on groceries in the UK. Independent shopkeepers say their livelihoods are endangered by out-of-town and convenience stores. Greenpeace and Friends of the Earth complain the big grocers air freight too much food and encourage intensive agriculture. The anti-poverty charities War on Want, Oxfam and ActionAid accuse the stores of driving down prices in the developing world and tolerating labour rights abuses.

Do they damage the environment?

The supermarkets' policy of supplying cheap food all year round regardless of the seasons clashes with the environmentalists' best practice of eating local, seasonal food. Stores import food from thousands of miles away, such as apples from Chile or peas from Kenya. Similarly, the big stores truck vast amounts of food around the country, from suppliers to a few national depots then back out to stores, clocking up hundreds of miles in the process. Air-freighting one 225g punnet of strawberries from New Zealand generates as much CO2 as 11 school runs in the car, according to the National Consumer Council.

A Defra study published last year found food miles had risen by 15 per cent between in the decade to 2002 and 4 per cent between 2002 and 2004. The stores give away an estimated 10 billion plastic bags a year and campaigners complain about excessive packaging.

In a National Consumer Council rating in September last year, no grocer scored an A on the environment. Waitrose was the best with a B; followed by Marks & Spencer and Sainsbury (C); Asda, Co-op and Tesco (D); and Morrisons and Somerfield (E).

Stores have announced action plans to lessen their environmental impact. Tesco plans to halve carbon emissions from its stores by 2020. Asda has a target to cut packaging by 25 per cent and is experimenting with wind turbines. M&S has a £200m, five-year plan to become carbon neutral. All the major grocery chains have signed up to the Courtauld Commitment to reduce the volume of packaging by 2010.

What about farmers?

The NFU accuses supermarkets of "screwing down" prices to farmers. Suppliers complain- mostly in private for fear of reprisals - that they are forced into one-sided contracts that can be cancelled instantly by the chains. Some are asked by the chains for lump sums as "retrospective discounts" in order ensure that their contracts are not terminated. Dairy farmers are "in meltdown", according to the NFU's new leader, Peter Kendall.

Experts say the public must decide whether they wish to pay more in order to support a network of small mixed farms that populate the countryside with picturesque black and white cows. Or if they prefer a cheaper, more intensive, barn system.

Supermarkets have also been accused of increasing the likely spread of Avian flu and of raising cruelty by intensifying poultry production and buying from farms where tens of thousands of chickens are crammed into a single shed. Farmers complain the stores import meat from countries where animal welfare standards are lower. The retailers reply that consumers are price conscious and warn that British farms must compete in global markets.

How has the high street fared?

Supermarkets have undoubtedly killed off thousands of independent butchers, bakers, fishmongers and grocers in the past 20 years. An inquiry by the All-Party Parliamentary Small Shops Group, which reported last year, found 11 per cent of independent shops, about 5,000, had closed in just five years since 2000.

The MPs warned that if supermarkets continued their growth unchecked, by 2015, independent grocers, petrol stations and newsagents were unlikely to survive. They expected rural shops and bakers to survive and gave post offices a "moderate chance" of survival.

Friends of the Earth argue that store groups have far more power than councils in the planning process because of their willingness to appeal decisions. Supermarkets argue they have brought choice and vitality to the high street by opening convenience stores, such as Tesco Express. Many people prefer these stores to their predecessors saying they are cleaner, cheaper and better stocked.

How is their record on health?

Patchy, according to campaigners. While supermarkets have presented the public with an extravaganza of fresh produce from strawberries to broccoli all year round, they have also pioneered ready meals and made fat profits from other junk food. In November 2005, the National Consumer Council found that supermarkets were running twice as many promotions for fatty and sugary foods as for healthy ones.

Tesco and Morrisons have angered the Food Standards Agency by boycotting the traffic light system for front-of-pack labelling, part of the Government's campaign against obesity, in preference for their own system based on Guideline Daily Amounts. Research by the Food Standards Agency and Which? suggests that people find the red, amber and green indicators of traffic lights much easier to understand.

What are their advanatages?

An average supermarket store offers 42,000 products and allows busy families to do one weekly or fortnightly shop under one roof, in a single, easy, go.

Supporters say this is helpful because mothers now commonly work and cannot shop daily as they did in the Sixties or Seventies. Competition between supermarkets has lowered prices (though street markets remain cheaper for fruit and vegetables).

In the interim report of its investigation into the grocery sector last month, the Competition Commission said that between 2000 and 2006, during a time in which supermarkets were rapidly expanding, real prices for food fell by 7.3 per cent.

During the same period, the grocers increased choice in their stores, increasing the number of product lines by 40 per cent. Campaigners say that such cheap food comes at a price - a social and environmental price totted up in obesity, climate change and weaker local communities.

Should we shop at supermarkets?

Yes...

* Supermarkets offer unrivalled choice with tens of thousands of product lines in a single shop

* Competition between the grocery chains keeps costs to a minimum and forces down prices

* Supermarkets offer consistent levels of customer service and respond quickly to public concern

No...

* Chain stores are diminishing diversity on the high street and driving out traditional and family traders

* Animal welfare and labour standards are lowered by the supermarkets' obsession with cheapness

* Flying in fresh produce out of season worsens climate change and weakens the market for local, seasonal produce

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