Where you shop can have a significant impact on your health, according to a National Consumer Council (NCC) study.
Nine supermarkets took part in the study
The NCC scored the UK's top nine supermarkets on the nutritional content of foods, labelling, healthy eating promotions and customer advice.
Waitrose, Sainsbury's and Co-op topped the table, while Asda, Somerfield and Morrisons brought up the rear.
The criticised retailers rejected the findings, saying the report was "a million miles" from reality.
Report needs 'health warning'
Somerfield said it was "surprised and disappointed by this research".
Somerfield said it is planning to reduce salt content in food gradually over five years "otherwise consumers will not be willing to accept the dramatic change in taste and will simply compensate by adding their own salt".
Morrisons pointed to its "Eat Smart" range of products, and the prominent display of fruit and vegetables in most of its stores.
Asda said the NCC report should "come with a health warning - it is about a million miles away from all the work we're actually doing to help improve the diet of our 13 million customers".
Asda also said it had reformulated the contents of its entire budget-priced food lines since the report was researched in June this year.
Tesco, meanwhile, argued that it was "the first supermarket to undertake research into how to provide better front-of-pack nutritional sign-posting" for customers, but promised "to work hard to provide clearer nutritional information and healthier products."
What makes healthy food?
But according to the NCC even those supermarkets that scored well were told they still had some way to go in promoting healthy eating amongst shoppers.
The NCC's Health Responsibility Index assessed supermarkets on the following criteria:
How healthy was the nutritional content of ten own label processed foods
How clear was the labelling on foods, whether unhealthy foods were signposted or not
Whether there were in-store promotions of healthy food such as fruit and vegetables
- Availability and quality of in-store information on healthy eating.
How the supermarkets fared
Waitrose 6.5 out of 10
Sainsbury's 5.5 out of 10
Co-op 5 out of 10
Marks & Spencer 4.5 out of 10
Safeway 3.5 out of 10
Tesco 3.5 out of 10
Asda 3 out of 10
Somerfield 2.5 out of 10
Morrisons 2 out of 10
Source: National Consumer Council
Tesco the UK's largest supermarket chain lost points due to the high salt content of some foods and lack of in-store advice on healthy eating.
However, arch-rival Sainsbury's scored well and was commended for the quality of customer information and for removing snacks from checkouts.
Waitrose was deemed the UK's healthiest supermarket chain according to the NCC study.
However, supermarkets which are widely seen as focusing on offering low prices - Asda, Morrisons and Somerfield - all did poorly in the survey.
"It's worrying that we found retailers with a high proportion of lower income shoppers appearing to reinforce the health inequalities between rich and poor," said Deirdre Hutton, the NCC's chair.
Ms Hutton added that the one exception to this was the Co-op, which was ranked third in the survey.