Marks & Spencer has been rated the most ethical food retailer by consumers for a second year, while Tesco was down five places on last year in 15th position.

M&S was rated 'good' or 'very good' by 60% of the 1,067 people polled in the Ethical Reputation Index, coming second overall behind Boots. The consumers were asked to rate 50 UK retailers on their treatment of environment, employees, customers and suppliers.

Despite the launch of its £100m environmental programme in January, Tesco was ranked 15th. Sainsbury's came 11th, Morrisons 20th, and Asda 14th.

The big four were also outranked by both The Co-operative Group, which came fourth, and Waitrose, voted 7th most ethical retailer.

Marks & Spencer was also a top performer in the National Consumer Council's annual league table that grades eight major chains on environmental policies. It was awarded a 'B' in the Green Grocers report, as were Waitrose and Sainsbury's.

Asda and Tesco were praised for improvements in performance over the past year, as the retailers moved from a D to C, while Morrisons and Somerfield moved from E to D.

However, no retailer "had yet risen to the challenge of being a truly green business", according to the report, which said supermarkets had to improve on the proportion of UK in-season produce on sale and reduce packaging and plastic bags.