The high street is enduring a slowdown that many predict could be the worst that the retail sector has seen for 30 years. With spiralling cost inflation, intense pressure on profits and growing fears of widespread job cuts, it hardly seems the time for a price war.

Yet Britain’s supermarkets are acutely aware that they have no other choice but to champion their value for money - or risk an exodus as cash-strapped customers go shopping elsewhere.

The sales growth at the likes of Aldi, Lidl and Iceland is the clearest indication that the credit crunch has sparked a change in Britons’ shopping habits.

Fifteen years ago most of Middle England would not wish to have been seen in discount outlets, but in this climate many are being adventurous and boasting about their bargain buys. Sainsbury, known for its quality food and drink, revealed last week the slowest sales growth out of its main rivals, while Bradford-based Morrisons is growing at almost double the pace.

Waitrose and Marks & Spencer have both profited from the spending boom in recent years and cashed in on a hunger for parmesan twists or melt-in-the-middle chocolate puds.

Yet even Marks & Spencer, the bellwether of the middle classes, has been pushing its price message in recent weeks with a ‘Dine in for two for £10’ television advertising campaign.

Until now, each of the grocers have been engaged in this low-level guerrilla warfare, running seasonal promotions or highly publicised one-offs such as Asda’s 2p sausage.

Rival executives fear a serious fight between Tesco and Asda more than any other clash. Both have deep pockets and could cause serious damage to the profit margins of their competitors in the event of an all-out price war.

Both have been sizing each other up in recent weeks with a range of tactical price cuts in a high stakes game of chicken.

This weekend’s new promotions, though, suggest that a serious contest is about to break out. And the main beneficiary will be the consumer.