A supermarket chain that owns five stores in Brighton and Hove and 47 across Sussex yesterday denied it had a stranglehold over the grocery market.

Tesco - whose shops range from Extra hypermarkets to Express convenience stores - rejected claims its 31 per cent share of the market was stifling competition.

In a 28-page document to the Competition Commission, Tesco claimed the public body's calculation methods and definition of "local" were flawed.

Tesco's report said markets should now be defined by a drive-time radius of 30 minutes or more - three times the 10 to 15 minutes used by the commission.

And it said 98.6 per cent of shoppers now had access to stores run by the five largest chains.

The supermarket argued the grocery market was now "national"

and not local, as shoppers increasingly bought online and were prepared to travel further to visit a store.

Tesco said: "We do not vary our retail offer in line with levels of local competition.

"We and all the other major grocery multiples have national strategies on pricing, branding, advertising, quality, range and service.

"The way in which customers do their grocery shopping has changed.

"Customers are now doing different types of shopping trip in different types of stores - from farmers' markets to the internet - with the result that smaller stores now impose an even greater competitive constraint on larger stores."

The claims were dismissed by Tony Mernagh, executive director of Brighton and Hove Economic Partnership, who accused the retailer of "bleating".

He said: "Tesco clearly has aspirations to be much more than just a grocer. Its European model is to have a supermarket on the ground floor and a department store on the top floor and it won't want the Competition Commission stopping it doing the same thing here.

"I would contest that there are many people who travel 30 minutes just to go to the supermarket - but if you effectively become a department store, I suppose they would."

The Office of Fair Trading referred the grocery sector to the commission in May last year after evidence suggested some chains were stifling competition by pricing products below cost and using banks of unused land to stop rivals opening stores.

Tesco's defence comes in response to the commission's initial "emerging thinking" document, released in January.

At the time, Trevor Freeman, secretary of the Brighton and Hove branch of the Federation of Small Businesses, said the supermarkets' smaller stores were the real problem.

He said: "It is ... their Express and convenience outlets that pose the biggest threat to the small shops because they are going head to head - but with the buying power and the marketing budget of a national chain."

Tesco has a 31.3 per cent market share, recent figures revealed. The commission is to publish preliminary findings in June, with a final report due in November.