DAVID SIMPSON, owner of the Something Special coffee and sandwich shop in Bicester, is angry.

The Oxfordshire market town that he has made his home and workplace is nicknamed Tesco-town – and not without reason. It has six Tesco stores, one for every 4,800 residents.

The Competition Commission unveiled proposals last week to shake up the planning laws to prevent a repeat of such dominance in any one area, but Simpson insisted that it was too little, too late.

“It is shutting the stable door after the horse has bolted,” he said. “It won’t do anything in the short term and it won’t do anything in the long term. There are no longer as many opportunities and nor are there sites available to increase the number of new fascias in this country.”

Simpson, a former president of the local chamber of commerce, said that locals in Bicester are forced to drive to neighbouring towns such as Aylesbury if they want to shop at a large rival supermarket. The only competition in Bicester at present is a Somerfield store. A new Sainsbury won’t open until 2009.

“People are driving out of Bicester because they can’t get choice and competition. That means they aren’t spending money in the town – some are just bypassing it altogether.”

Like many other Tesco critics, Simpson feels that last week’s Competition Commission report into supermarkets let Tesco off lightly.

Even the company’s City supporters agreed that the outcome of the commission’s 18-month inquiry into supermarkets could have been far worse for Britain’s largest food retailer. After all, it concluded that Tesco’s market share was not so dominant that it dented competition and it gave its burgeoning convenience store portfolio the all-clear. Among its shareholders, there was a collective sigh of relief and Tesco shares hit an all-time high.

James Anstead, retail analyst at Citigroup, even headlined his note to investors on the report: “Preliminary findings should reassure on Tesco.”

And Tesco itself welcomed the findings, but gave warning that it would study any possible remedies to ensure they did not create any “perverse effects”.

But is this too rosy a view of the likely impact of the commission’s proposals on Tesco?

There are several key areas where Britain’s biggest retailer is likely to feel the impact of the changes now being suggested – and where the impact could be greater than on its rivals.

The Competition Commission suggests that when considering planning applications, councils should take into account local competition.

In other words, if Asda, for example, has a stranglehold on supermarket shopping in a particular town, then planners should be able to discriminate against Asda when considering applications to build further stores. An application from a Sainsbury, Tesco or Morrison should be favoured.

The stark and simple fact is that, at the moment, Tesco is Britain’s biggest supermarket group by a mile; in the so-called one-stop grocery shopping market, Tesco takes around one pound in every three that goes into the tills. In more than two-thirds of Britain’s postcode areas, the company is the largest operator.

So if planning ministers follow through with the Competition Commission’s idea of making councils take local competition into account when looking at planning applications, Tesco is likely to face the greatest constraints on opening new outlets.

Its rivals should have an easier ride, simply because they currently hold a dominant position in far fewer areas.

Take a place such as Dumfries and Galloway. Tesco is thought already to have about 50% of the one-stop supermarket space in the area. But more importantly, it has a big landbank there – far bigger than any of its rivals. If all the operators were to build on their development sites, Tesco’s share of supermarket space would reach 68%.

Take another example: Uxbridge. Tesco already has two-thirds of one-stop shopping space there. Developing all known superstore sites in the area would lift its share to more than three-quarters.

Certainly, there are some areas where other operators are strong. Asda has 46% of space in Bolton. Sainsbury has 63% in southwest London and 52% in Harrow. But in none of these cases would developing sites in the pipeline increase the dominant operator’s grip.

Planning experts believe the changes could allow the big four supermarkets to get their hands on hundreds of new sites. Analysts predict that Asda, to take an example, could grow by half as much again – opening as many as 150 new stores.

Tesco’s Lucy Neville-Rolfe lambasted the plan for a fascia or competition test: “Such a so-called competition test would serve only to reduce competition for sites. It would, therefore, in effect be an anticompetition test. Retailers not as popular with customers as Tesco might be preferred by the test. Indeed, in some areas the only beneficiaries might be the more expensive retailers.”

The Competition Commission has also suggested there should be a review of the so-called needs test, which puts the onus on local councils to prove the need for a new supermarket.

It has also suggested a possible relaxation of the rules to make it easier to open new stores on edge-of-town sites.

When combined with the competition or fascia test, this could again damage the largest operator by giving rivals a better chance to open new stores.

Planning experts said it could have even more profound consequences – insisting that the reduced competition combined with an easing of planning restrictions on edge-of-town sites, will dent town-centre land values, possibly by 10% or more.

Ian Anderson, head of UK retail and leisure planning at CB Richard Ellis, the world’s biggest property consultant, said: “The losers will be the developers of town-centre sites. This will certainly impact on land values.”

Anderson said that many of Britain’s biggest landowners, such as Hammerson and Land Securities, the FTSE 100 property groups, own big portfolios of in-town, edge-of-town and out-of-town properties and so won’t necessarily be hard hit by the changes.

The Competition Commission chairman Peter Freeman last week played down the possibility of forcing supermarkets that are dominant in an area to sell off existing stores. It would, he said, be a remedy of last resort and the commission hinted that if it did happen, it would involve only between 10 and 40 stores.

A spokesman for the commission said: “There has been quite a focus on the possibility of land divestments from some quarters, but it’s worth bearing in mind that we are talking about a small number of areas.

“Changes to the planning system would have a more lasting effect on decisions and developments across the whole country in this sector.”

But what about the supermarket chains’ landbanks – sites as yet undeveloped but where new stores could be built?

This is an area where Tesco also seems to be vulnerable. It may be Britain’s dominant supermarket group in terms of sales. But the scale of that dominance can only increase if all the known undeveloped superstore sites are built on.

There are no official public figures to show which grocery chains own what. But research by The Sunday Times and Channel 4’s Dispatches published ear-lier this year shows that, astonishingly, Tesco controls more sites capable of taking a 15,000 sq ft supermarket than all its rivals put together.

The company has been far more proactive and successful than its competitors in building up a development pipeline – and it shows.

Tesco is reckoned to control about half of all the development sites in Britain; Asda probably has about one quarter. Sainsbury – whose development programme stumbled in the early years of this decade while the company struggled to sort out enormous problems with its day-to-day operations – has less than 10%. Morrisons’s share is also thought to be less than 10%.

The Competition Commission said it had concerns about 110 sites – sites where there was some suspicion that they are lying undeveloped, bought by one company to keep out rivals rather than to be built on. All the supermarkets, including Tesco, deny they use land to stymie competitors.

The commission did not reveal which companies own the 110. But given Tesco’s powerful grip on development sites as a whole, it is reasonable to assume that the company must own a big share of them.

If – and it is a big if – there is to be forced divestment, then it would be a reasonable assumption that Tesco could stand to lose the most. Ferocious lobbying from the supermarket giant can be expected in the days and weeks ahead.

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