LOOKING for that exclusive solitaire diamond ring, or the latest super-efficient washing machine? Why not try your friendly neighbourhood supermarket?

Consumers look set to be the big beneficiaries of the latest attempt by supermarket giants such as Asda and Tesco to muscle in on territory that was once the preserve of high street retailers.

Asda claims its new range of jewellery - featuring everything from fashion jewellery at 97p to a diamond solitaire ring at £499 - will undercut the going rates in the high street by as much as one third. York shoppers will be among the first to benefit - with items from the extensive range of rings, necklaces, bracelets and watches expected to be on sale at the Monks Cross store from this August.

Tesco, meanwhile, is already predicting a fall in the price of electrical goods such as dishwashers and freezers with the launch at selected stores this week of its own in-store range. The supermarket estimates it will be able to undercut many high street retailers by tens of pounds.

Gold, silver, diamonds and fashion watches will be among the range of items on sale at Asda. A spokesman for the chain said prices would start at 97p for fashion jewellery, with diamond jewellery starting at £22.99 and the most expensive diamond solitaire ring retailing at £499.

The store will also offer a range of watch brands, including Timberland, Seiko, Baby-G and G-Shock. Prices of jewellery and watches across the range could be discounted by up to a third, the spokesman said.

The first Asda store to stock the range is at Horwich, near Bolton, Greater Manchester. But the number of stores offering jewellery will grow to 20 by the end of the year - with the Monks Cross store at York expected to be the second or third in the country to do so.

"York is going to be one of the first," the spokesman said. "The best guess at the moment is August."

Tesco, meanwhile, which already sells a number of smaller electrical items such as hair dryers and irons, says its decision to sell larger electrical goods such as freezers, dishwashers, washing machines and ovens follows a trial at a store in Bar Hill, Cambridgeshire.

Initially, the goods will be available only to customers at Tesco's largest Extra stores - the nearest to York is at Seacroft in Leeds.

But Richard Anderson, the supermarket chain's corporate affairs manager, said the aim ultimately was to roll the service out to other larger stores, such as those in York.

Among the 1,500 electrical household products on offer will be a 14in portable TV costing £63 and a 28in Nicam stereo TV for £170. A Hotpoint WMA30P washing machine will be available at £279.05 and an AEG FAV507000 dishwasher at £349.95.

Cheaper warranties and free delivery will also be offered at the Tesco Extra stores and the Tesco.com web site, the supermarket chain says.

But will the latest moves by the supermarkets really mean better choice and better value for the consumer? Or will it ultimately lead to reduced choice as giant supermarket one-stop shops monopolise the market and drive out small, independent retailers?

Asda insists its move into jewellery is not an attempt to muscle in on High Street jewellers' trade.

"Our aim is to offer customers the goods that they ask for. We think we can offer them a better deal than our competitors," said Mr Anderson.

Tesco also insists it simply aims to offer better value.

"We want to make sure everyone in the UK has access to electrical goods of all sizes at lower prices," said Tesco marketing director Tim Mason.

"Customers tell us they often find it difficult and confusing to buy big electrical goods. We want to make it easy for them, and eliminate any extra costs."

It's what you'd expect the supermarkets to say, of course. Roland Harris, of York Chamber of Commerce, however, said he believes consumers will still value the choice, variety and quality of service High Street retailers have to offer.

"It is not always just about where you can get the lowest price," he said. "This is a customer driven industry. But people will continue to want to shop in different ways." What High Street retailers will have to do compete, he said, is "emphasise service and after-sales support." In other words, precisely the things they are traditionally good at.

- Sainsbury's this week introduced a new range of 800 products designed for people needing a restricted diet or suffering from allergies. The food range includes raw ingredients, flour and cake mixes, breakfast cereals, corn pasta, gluten-free pizzas, wheat-free bread and dairy-free spreads.