Tesco and Asda are the price-cutters and they are the ones who have grown their businesses during the past five years

Tesco marketing director Tim Mason

Tesco, along with the UK's third-ranked retailer, Asda, believes in offering customers low prices across the range of goods they stock.

But Sainsbury and Safeway, the UK's number four, rely on bigger discounts on selected items.

A spokesman said Sainsbury's own wide selection of special offers - including buy-one-get-one-free deals on 50 different products - reflected a "constant, long-term approach to cutting prices".

And although the store has cut the cost of 3,000 items during the past year, managing director Stuart Michell says its customers consider quality and service to be "more and more" important.

But Tesco marketing director Tim Mason says most shoppers are looking for low prices first and foremost.

He told BBC News: "Tesco and Asda are the price-cutters and they are the ones who have grown their businesses during the past five years.

"Sainsbury and Safeway have tried different things and their businesses have not grown as fast."

It all depends on the products you pick - and that is where the confusion comes in for the consumer

Clive Beddall The Grocer

Tesco director John Gildersleeve says its price-cutting policy is also "helping keep a lid on inflation".

But Clive Beddall, editor of retail magazine The Grocer, told BBC News that during the past five years Asda's prices have been consistently lower - beating Tesco into second place.

That assessment is based on the cost of a "typical" weekly shopping basket containing 33 different items.

But as Mr Beddall explains: "It all depends on the products you pick - and that is where the confusion comes in for the consumer."