Retailers stampede for "green pound"

The Scotsman reports that retailers are rushing to capture the consumer's green pound. In the UK, New Consumer reports that Marks and Spencer ranks above other food retailers Tesco, Sainsbury's, Waitrose, Asda and Morrisons according to the Ethical Index. But the supermarkets are investing a lot in trying to catch up. But, some supermarkets are sending confusing messages. While there corporate sites are declaring their green credentials, in store customers are incentivised with 2 for 1 offers. Could they be accused of encouraging over-consumption?