This man will have them rolling in the aisles

Heather Tomlinson talks to Sir Derek Morris, the competition chief who holds sway over Safeway's supermarket suitors

Some men will say anything to get out of doing the weekly shopping. And when Sir Derek Morris, chairman of the Competition Commission, was first asked to investigate the supermarket industry four years ago, he had the perfect excuse. "At the time of the last inquiry, I did say to my wife: 'You realise that I couldn't possibly shop at a supermarket while this is going on. You'll have to do it'."

But she wasn't fooled. "It got me absolutely nowhere," he admits.

So there's little point Sir Derek trying the same trick this year as, once again, he leads an inquiry into the industry. This time, unlike the last, it is not a result of the "rip-off Britain" campaign. Instead, he is scrutinising the effects of a merger between Safeway, the fourth-largest supermarket chain in the UK, and any of the four companies interested in buying it: Wm Morrison, Asda, Tesco and J Sainsbury (a fifth, Philip Green's retailing empire, has already had a green light from the Office of Fair Trading). By August, Sir Derek must decide if the deals are in the public interest.

In the last inquiry, critics said he took a soft line. The supermarkets had to follow a new code of conduct governing their behaviour towards suppliers and farmers, but they were not found to be overcharging customers.

This time, Sir Derek can decide how many of Safeway's supermarkets can be bought by each buyer. The decision will determine the future of the industry.

While he cannot talk about the inquiry specifically, he does gives some pointers on what will be considered. The size of the companies' profits will not be taken into account. Instead, the Commission will attempt to predict what will happen if each buyer wins, compared to what will happen if it doesn't. It will consider the shape of the market if Safeway is left as it is, and also the potential effect of a successful buyer, such as Philip Green, who has a reputation as a tough cookie retailer.

The Commission will look at the minute detail of every Safeway supermarket's local area, to see how many others are in the vicinity and how long it takes to get to them. For each potential merger, the effect on hundreds of communities will be scrutinised and compared with consumer behaviour. "In the last report there was a mass of figures – who shops only at one supermarket, who shops around, do they do a subsidiary shop somewhere else? Gosh! It was mind- numbing," says Sir Derek. "But unless you get into that detail, which does not make an exciting read, you don't get to the facts of what it means for consumer choice."

The minutiae required means he faces a hugely demanding timetable. "We typically have three months to look at a merger. Here we have four mergers, with four and a half months to do it."

The Commission is also embroiled in another mega-merger investigation, that of Carlton and Granada, the two main ITV companies, although Sir Derek is not personally in charge.

However, he does have an inquiry into extended warranties on his hands. He is investigating whether companies like Dixons have a monopoly over the guarantees that are given on goods sold. The issue is a sore point for retailers, which can make a large chunk of their profits from the warranties.

High-profile probes like these mean 57-year-old Sir Derek wields a lot of power over UK plc. But he does not look like a man who revels in this status. Rather than being brought up in business, his background is in academia: he is a doctor of economics at Oxford University, where he will return when his post at the Commission finishes in 12 months' time. His manner is also friendly and cheerful.

But he is highly respected in industry. "The Competition Commission has become a bit over-theoretical recently, but generally it does a good job," says Dorothy Livingston, a senior competition lawyer at Herbert Smith. "I think very highly of Sir Derek. He is very clever, and hard working."

In June, Sir Derek's powers will be increased substantially when the Enterprise Act comes into force. Instead of acting as a government adviser, the Commission will become an independent regulator that can order businesses to behave if they are acting in an anti-competitive way. It will get more resources, and it is doubling its employees to 200.

The result, says Sir Derek, will be a better deal for the consumer. "You will see much more emphasis on open, effective, efficient, competitive markets, and that will have quite an impact on consumer choice and value for money."

In some ways, the Commission will have a narrower remit. Before, it judged whether a merger was against the public interest, a woolly statement that could include any number of problems. Now the only test is whether it leads to a "substantial lessening of competition", and Sir Derek has the final say, not a secretary of state.

Although some businesses are concerned about this, Sir Derek says the good guys have nothing to fear. "For efficient, entrepreneurial and dynamic companies, this is fairly good news," he explains. "If consumers have more choice and information, then people with ideas on what the consumer wants will have more opportunity to offer those products and develop their businesses."

His passion for competition has been matched by competition policy. In 1991, when he first became a member of the Monopolies and Mergers Commission, the forerunner for the Competition Commission, he says a monopoly would not be considered a bad thing per se – only if it could be proved to be bad. This changed in 1998, the year he was made chairman of the MMC.

With the extra powers in this year's Enterprise Act, any restriction of competition is considered a bad thing. "There is a much greater emphasis on the importance of competition for consumers and as a driver of efficiency and productivity growth in the UK economy."

This supermarket inquiry will be one of the last investigations done under the old regime, and one of the last big deals he will handle as he retires next April. A return to Oxford beckons, along with the weekly shopping trip.