Marks & Spencer is lagging behind its rivals in convincing shoppers of its ecological credentials - in spite of its huge efforts to position itself as a green retailer, exclusive research for The Grocer indicates.

M&S, which launched its £200m Plan A strategy earlier this year, was only considered the fourth-greenest supermarket by shoppers, according to Harris Interactive's poll of 2,000 people (see table right).

"Greenest" was defined as being the most environmentally conscious and making the biggest effort to reduce its impact on the environment. Tesco and the Co-ops tied for the top spot with 11% of the vote, with Waitrose third with 10%. M&S was considered greenest by 9% of shoppers, while Sainsbury's (6%), Asda (3%) and Morrisons (2%) were lagging even further behind. However, 48% said they were not sure which chain was the greenest.

"Plan A set out a list of things we could look at to become more environmentally friendly. Not all of them have worked, but they are just first steps. It's all about being transparent and building trust with customers," said Mike Barry, head of CSR at M&S.

In a separate survey for The Grocer to coincide with our Green Issues conference on Wednesday this week, Harris also found 67% of consumers were not aware of carbon labelling. But, once it was explained, 85% thought a carbon label on all products would have some influence over purchasing habits. Six in 10 consumers wanted to see more green products, and two-thirds expected to buy more of them in the future.

Nearly 60% believed suppliers were not taking the issue seriously and nearly 40% thought claims were a gimmick; 54% thought themselves "somewhat green" and 23% bought green lines at least weekly.