Food labels on Tesco products are confusing shoppers, a consumer group has claimed.
Tesco says its label system is more practical and informative
The supermarket giant has rejected the Food Standards Agency's (FSA) colour-coded "traffic light" nutrition guide in favour of its own.
But a Which? survey found only 86% of shoppers understood the Tesco labels, while 97% understood the FSA system.
Tesco admitted its own labels were more complicated but said they helped shoppers to follow a healthier diet.
A spokesman said: "While we understand that traffic lights may give a simpler initial impression, customers have told us that our system is more useful in taking practical steps towards a healthier diet.
"Sales data demonstrates that when nutritional signposts are added many shoppers switch to products which are lower in salt and fat.
"Traffic lights may never produce these results."
The FSA wants all firms to adopt the traffic light scheme
The supermarket is one of a number of firms to reject the FSA scheme, which uses red, amber and green to indicate high, medium and low levels of fat, sugar and salt.
But Which?, which surveyed 636 people for its study, wants all retailers and manufacturers to adopt it.
Chief policy adviser Sue Davies said: "It is confusing for consumers if our supermarket shelves are full of different, contrasting food labels."
Earlier this year, several food giants including Kraft, Danone, Kelloggs, Nestle and PepsiCo, signed up to a rival label which shows guideline daily amounts (GDA) of key nutrients.
Dr Jane Holdsworth, representing the firms, said the GDA scheme was an "at-a-glance aid for shoppers irrespective of the supermarket they go to".
She added: "Far from 'going it alone' as Which? asserts, this consistent labelling scheme will be on thousands of leading products by the end of 2006, making it by far the dominant scheme in shops.
She added a multi-million pound education campaign to help inform customers about the GDA scheme is being planned for this winter.