The Co-op has begun a trial identifying branded foods which have high levels of fat, salt and calories, using shelf cards which it said would "demystify" the nutritional values of all products its sells.
The cards take a 'traffic light' approach by calling salt and fat contents high, medium or low. They also give calorie contents.
The move comes ahead of a government white paper on health, which is expected to introduce controls on foods and their promotion. The health secretary John Reid is understood to have insisted on the use of traffic light labelling.
The white paper was expected this month. However, sources have suggested that it could be delayed by months. Linked government guidance on health and nutrition is also expected to be delayed, perhaps until next year.
The Co-op scheme is the first such labelling of branded goods. Tesco launched a similar scheme last month for its own-label products. While manufacturers have reduced salt and fat in some products, none has clearly informed customers about the amounts in products, the Co-op said.
The Co-op has labelled over 300 own-label and branded biscuits, cereals, yoghurts and desserts in 10 stores in London and Glasgow in the trial, which is expected to last a few months. It will pass its findings on consumers' buying responses to the Food Standards Agency.
Branded products include Premier Food's Loyd Grossman Green Thai Curry Sauce, whose fat and salt content the Co-op has labelled high, Kellogg's Cornflakes and Nestlé's Shreddies.
The Food and Drink Federation called the move too simplistic: "We need to be careful not to add more confusion by adding yet another labelling system before the FSA has finished researching this area."
Food Manufacture's sister magazine The Grocer has begun a campaign against such labelling, which it says could demonise otherwise healthy products because of its over-simplistic approach.