The shopping trolley, derided for its wobble and failure to steer in a straight line, is seen as a new weapon to fight the nation’s obesity crisis.

Technology experts have devised an “intelligent” trolley that will alert shoppers when junk-food items are dropped in. Barcodes on foods high in fat, sugar and salt would trigger red warning lights on an interactive screen. Eventually, barcode information may be passed to mobile phones.

The trolleys are also seen as the way forward to cut down on food packaging. In the future, most information about a product could appear on the computer screen attached to the trolley. Besides nutrition and country of origin, the screen would say if the packaging could be recycled. Essential information about contents that trigger allergies, such as nuts, would remain on the packaging.

The new trolley concept is to be unveiled in London tomorrow by the Institute for Grocery Distribution (IGD) at its annual conference on the future of retailing in Britain. A trial is already under way using “intelligent” trolleys at Stop & Shop stores in the United States.

The technology does not yet help shoppers to choose a healthy diet. However, the trolleys will point the shopper to best buys of their favourite items or promotions that suit their life-style, and even give directions around the store to locate an item.

The trolley is primed by information on a shopper’s loyalty card. Once the card is scanned, the touch-screen reader on the trolley knows whether the shopper is a single person or someone doing the big weekly shop. It may also know if there is a diabetic or dieters in the family. With a record of previous purchases, it could then direct the shopper to best buys and deals suited to individual taste.

The barcode of each item going into the trolley must be scanned for a shopper to have access to the information. Touch-screen icons will then appear and the shopper will decide if the information is required.

Sion Roberts, director of consumer industries and retail at EDS, the technology company, is confident that these trolleys could play an important role in helping people to choose healthier foods and to resolve the issue of waste packaging.

He said: “Everyone wants more and more information and different information, not everyone wants to know everything about a product.

“But many shoppers already think that lists of ingredients on packaging are too complicated to read and understand. It will be easier to read larger print on a screen. There will also be red-light alerts if you ask the trolley to give your shopping a health check. It may not stop you putting a box of cream cakes in the trolley but you will be made to think about the decision.”

Mr Roberts believes that the device also has potential for use in DIY stores, in chains such as Ikea and for couples drawing up a wedding list.

Similar technology is already being used by the Department for Work and Pensions on touch screens in Job-centres to help to match the unemployed with vacancies.

Mr Roberts said: “I cannot see a different way of resolving the issue of packaging waste. Something is going to have to give and technology can help reduce packaging yet still give consumers the information they need.”

There is some excitement among retailers because consumer research by EDS has found that 30 per cent of shoppers say that they would like to use the technology now.

One in five shoppers is content for retail companies to “spy” on their past purchasing record, dietary preferences and information on family allergies or medical conditions to help direct them to healthier produce.

Only the over65s were resistant to such gadgetry for shopping. They thought that it would be time-consuming and complicated to use. But some 70 per cent of 18-34-year-olds had no qualms in letting supermarkets see personal information.

EDS has already worked on minimising theft of the screens on the £160 smart trolleys.

Gerardine Padbury, senior analyst at the IGD, said: “Young people are comfortable about giving away information about themselves. Just look at the social networking sites where people are telling their whole life story to strangers.

“By giving information to supermarkets they may be persuaded to buy a healthier shop.”

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