Products will be given low, medium or high ratings

Cards on the shelves of 10 stores in London and Glasgow will show if levels in about 300 major brand products such as cereals are high, medium or low.

The Co-op will then pass on its findings to the Food Standards Agency.

But the Food and Drink Federation, which represents manufacturers, says the Co-op risks oversimplifying matters.

Spokeswoman Kate Snowden told BBC News Online the industry was already working with the Food Standards Agency on how labelling could be improved.

"Simply by saying this product is high in fat doesn't take into account individual requirements or your entire diet," she said.

SOME CO-OP LABELS Loyd Grossman Green Thai Curry Sauce: Salt 1.5 (high), fat 6.4 (high), calories 104 Co-op Madras Cook in Sauce: Salt 1.3 (high), fat 8 (high), calories 115 Kellogs Ricicles: Salt 1.0 (medium), fat 0.7 (low), 382 calories Kellogs Cornflakes: salt 2.4 (high), fat 0.9 (low), 371 calories Nestle Shreddies: salt 1.0 (medium), fat 1.9 (low), 350 calories *Per 100g

"I think we need to be careful that, when we are trying to give customers more information, we're not confusing them."

The Co-op will label goods ranging from biscuits and cereals to sauces and yoghurt on a variety of names including Loyd Grossman, Kelloggs and Nestle.

It will use customer exit polls and sales figures to gauge consumer reaction to the labelling.

Speaking on BBC News 24 spokeswoman Christine Clarke said the scheme was aimed at making customers' access to nutritional information easier.

"Our customers are much more concerned nowadays about their fat intake but we wanted to make that information easy to understand, more upfront and also across all products.

"Using a system which is high, medium and low, puts it in context, makes customers make easier, better choices."

Government intervention

Liberal Democrat health spokesman Paul Burstow told Radio 4's Today programme his party would like to see the Food Standards Agency building on the Co-op idea.

He advocated a colour-coded traffic light labelling scheme.

"I think what we need to see now is the Food Standards Agency taking forward this idea of traffic light labelling... and making sure the scheme is clear and consistently applied across all food products, across all companies.

GUIDELINE DAILY AMOUNTS Salt: 5g for women, 7g for men Fat: 70g for women, 95g for men Calories: 2000 for women, 2,500 for men *Source British Nutrition Foundation

Mr Burstow said the government might have to intervene if manufacturers refused to reduce high levels of fat, sugar and salt in products.

"If they're unable to respond to pressures within the market - and there is clearly consumer pressure now to see reductions in these areas - then government may well have to step in."

But he said a traffic light labelling system would "put an immense amount of pressure on the industry".

"There aren't going to be many manufacturers of food that are going to want red lights on the foods that are being served up."