Supermarkets are more likely to promote unhealthy foods than fresh produce, the National Consumer Council has found.
The Food Commission surveyed nine stores in June and July
Its survey of 2,346 price deals at nine supermarket chains found none met the NCC's target of offering 33% of promotions on fruit and vegetables.
But the NCC praised retailers for reducing displays of "unhealthy" snacks at checkouts and said they had made progress on its best practice targets.
The consumer watchdog rated the Co-op top in its health responsibility index.
HEALTH RESPONSIBILITY INDEX
1 The Co-op
2= Marks and Spencer
*Source: NCC Healthy Competition report
The index assesses retailers on their approach to salt reduction, nutrition labelling, in-store promotions and customer information.
The Food Commission, on behalf of the NCC, conducted spot-check surveys of one store per supermarket chain in England in June and July.
Every retailer surveyed, except Marks and Spencer, had more than double the deals on "fatty and sugary" foods than fruit and vegetables.
Twenty-seven per cent of Marks and Spencer's deals related to fresh products, compared with 7% at Somerfield and 9% at Morrisons, the Healthy Competition report said.
The NCC said the good news was that supermarkets were starting to compete on health issues.
Chief executive Ed Mayo said: "The fact that the Co-op has an above-average share of budget-conscious shoppers shows that this is not just for the better off.
"But we're dismayed that the biggest supermarket - Tesco - is a laggard on health."
The watchdog rated Tesco sixth, after a "modest overall improvement" on its performance last year.
Morrisons was placed at the bottom of the index, despite a "slight improvement" on salt and nutrition labelling.
In a statement responding to the Healthy Competition report, the supermarket chain said:
"The National Consumer Council's report is inaccurate and does not present a true reflection of our approach to 'health responsibility', failing to recognise the progress we have made.
"We have introduced our Eat Smart healthy eating range and extended our Better Because brand, in addition to an ongoing robust salt reduction programme focused on the most popular products sold in stores."