Environmental sustainability has become a mainstream concern for the UK's supermarkets, with all the major chains investing heavily in improving their green credentials, according to a new report from the National Consumer Council.

The report, which analysed and ranked the environmental practices of the UK's eight largest food retailers, found that the widely held perception that green products and policies are solely targeted at affluent shoppers is increasingly outdated, with lower-end retailers now embracing a greener approach.

Sainsbury's shares the title of greenest greengrocer with M&S and Waitrose, all of which received a B rating in the NCC's rankings. Meanwhile, Asda and Tesco moved from a D to a C ranking and Morrisons and Somerfields improved from an E to a D.

Report author Lucy Yates said that the rankings had been based on the supermarkets' progress in limiting their carbon footprint, cutting down on waste and packaging, and embracing sustainable sourcing strategies. "The aim of the report was to replicate the consumer experience as much as possible so we collected all the data in-store and focused on criteria where supermarkets can help customers make greener choices," she explained.

Larry Whitty, chair of the NCC, said that the research proved that "all stores [are] now beginning to embrace sustainability". The organisation pointed to steps by Asda to provide "Smart Price" value fish fingers sourced from sustainable fish stocks as evidence that environmental best practices are increasingly being embraced as standard rather than being reserved for higher value products.

However, Yates warned that with none of the supermarkets attaining an A grade under the NCC's criteria there is still a great deal of room for improvement, particularly in retailers' waste policies.

"Government and industry have already announced that they will reduce the overall environmental impact of carrier bags by 25 per cent by the end of 2008 and phase out non-efficient light bulbs by 2011," she said. "But to really make a difference, we want to see supermarkets go much further than this by making energy-efficient lights much cheaper now and phasing out plastic bags completely."

She added that with consumers typically interested in reducing their environmental footprint but unclear on how best to do so the onus was on supermarkets to phase out unsustainable products and practices. "People want to be greener but it is difficult to analyse greener choices when you just want to get the shopping done," she observed. "That's why we want the supermarkets to 'choice edit' and simply get rid of the least sustainable products."

The British Retail Consortium welcomed the report's findings and predicted further green improvements amongst the leading supermarkets. "Consumers are increasingly aware of factors beyond price and availability and are interested in environmental factors," said a spokesman for the trade group. "Green has become a deciding factor in purchasing decisions and we are going to see enormous competition between the biggest retailers."

He added that smaller retailers would also have to fall into line with the current green retail trend arguing that while they may lack the resources to implement widespread changes to their business they would risk losing out to the larger players if they failed to embrace more sustainable business models.