ASDA's environmental performance has worsened in the past two years, making it the least green of the five major supermarket chains, according to a report from a publicly funded consumer watchdog.
Consumer Focus complained that Britain's second biggest supermarket chain stocked only a small proportion of sustainable fish and sourced a "dismal" 59 per cent of fresh produce from Britain, a seventh less than 2007.
Among other problems, Asda had reduced its range of organic produce by 38 per cent and was making little use of packaging certified by the Forest Stewardship Council, according to the report, Green to the Core?
In a rating from A to E, the survey downgraded Asda from a C two years ago to a D – the same as Aldi and Lidl.
Britain's biggest retailer, Tesco, "showed no progress since 2007", warranting a C along with the Co-op and Morrisons, according to Consumer Focus.
For the first time since the supermarket rating was launched by its predecessor, the National Consumer Council, three years ago, the top A score was achieved – by Marks & Spencer and Sainsbury's.
M&S had put doors on all freezers and was excelling on Fairtrade and animal welfare, while Sainsbury's scored highly on packaging, organics and sustainable fish.
Waitrose, which had the highest proportion of home-grown fresh produce on sale, 92 per cent, maintained its B rating.
Consumer Focus carried out checks of stores belonging to the chains in Manchester in July, when it said there was ample scope to stock local fruit and vegetables.
Assessors checked the availability and promotion of fresh produce, organics, higher welfare meat and eggs and sustainably sourced fish, and action on climate change and packaging.
Lucy Yates, the report's author, challenged supermarkets to help customers of all budgets to shop green by running money-off promotions and displaying recipes for seasonal British produce such as spinach and courgettes.
"Shopping green should not be hard," she said. "Our survey shows that when a grocer has the will to respond to consumer pressure on green issues, this works through to the shop floor."
Asda, owned by the US grocery giant Walmart, responded angrily to the report. "The Consumer Focus report Green to the Core? isn't worth the recycled paper it's written on," said Asda, which has 16 per cent grocery market share. "It's inaccurate and misleading."
The supermarket said that sourcing some products in the UK reduced emissions, and pointed out that it had cut carbon emissions in existing stores by 20 per cent since 2005 and slimmed down packaging.
Lidl said it was disappointed with its score, saying it had never given away plastic bags, did not air-freight fresh produce and recycled most store waste.
Aldi said it was continuing to test energy-saving measures, while offering customers "high quality products at low cost prices".
Friends of the Earth's supermarket campaigner, Helen Rimmer, claimed the report showed that some retailers were guilty of exaggerating their green credentials.
"Despite shouting loudly about their green initiatives, some of the biggest supermarkets are still failing to put planet-friendly food on their shelves," she said.
She called for the Government to create a supermarket watchdog, a recommendation of the Competition Commission's final grocery investigation last month.
How green is your supermarket?
A: Marks & Spencer; Sainsbury's
C: The Co-op; Morrisons; Tesco
D: Asda; Aldi; Lidl
A is most green and E least green. Source: Green to the Core? Consumer Focus