Marks & Spencer is lagging behind the big four supermarkets when it comes to improving the green credentials of its packaging, according to new research.

The packaging of own-label products including ice cream, mushrooms and bacon were all heavier than those of supermarket rivals, consumer body Which? has found.

The move comes despite the retail giant’s high-profile ‘Plan A’ campaign to become more environmentally friendly, which led to M&S charging shoppers for its carrier bags.

For the study, Which? bought 27 own-brand items from supermarkets Tesco, Sainsbury's, Asda, Waitrose and Morrisons, including fresh and frozen food as well as washing up liquid and fizzy drinks, and weighed all the packaging.

It found that in total M&S packaging, including labels, totalled 415g, while Sainsbury's came in the lightest at 369g, just ahead of Tesco on 370g, and came to the conclusion that retailers need to keep doing more to cut excess packaging.