Tesco, Asda and Sainsbury’s have begun the big battle for customers in 2009 by embarking upon the fiercest supermarket price war yet.

After a tough six months, during which consumers found their budgets stretched to breaking point, the ‘Big Three’ have said they are determined to offer their Northern Ireland patrons the best possible deals.

Tesco threw down the gauntlet to retail rivals yesterday after it slashed prices on 3,000 staple products and promised to invest £100m this month in a combination of permanent price cuts and promotions.

The leading grocer said it planned to launch a new advertising campaign today, which will compare the cost of customers' baskets of shopping against the prices of its competitors.

The move comes just four days after this newspaper predicted a credit crunch price war between retail giants would characterise the beginning of this year, after a dire 2008 marked by high food and fuel prices for householders across the province.

Gary Mills, director for Tesco in Northern Ireland, said the cost of shopping this year will be more important to customers than it has ever been.

“For years retailers have made claims and counter claims about who is the cheapest. But until now nobody has looked at what shoppers actually put in their shopping baskets to provide a true picture of what customers are really spending. Our new real baskets look at the actual products people buy every day including popular own brand items and essentials such as own brand milk, meat, fruit and vegetables so customers can be confident that our price claims reflect real shopping.”

Asda has already announced a new wave of discounting on thousands of items, including fresh food and household products this month.

The supermarket said 100 frozen food products and 200 everyday health and beauty lines, such as shampoo and deodorant, would be sold for £1.

It also said it guaranteed that at any one time there would always be 1,000 items with reduced prices, although some fresh produce would vary according to season.

Andy Bond, the retailer’s president and chief executive officer, said: “2009 is going to be a very difficult year.

“I believe we have an obligation to help our customers through these tough times. Frivolity is out and frugal is the new cool as customers change their shopping habits in order to make ends meet.”

Sainsbury's has also joined the new year price competition, vowing to grow its Basics range to more than 600 products by the end of January.

The supermarket said more than half of these products would be priced at less than £1.

A spokesman for Sainsbury’s said: “This is our way of helping our Northern Ireland customers help manage the economic downturn without any compromise in quality.”