Asda and Sainsbury's have come under attack from green groups over their excessive use of plastic bags in home deliveries.
Environmentalists have accused the chains of using an unnecessarily large number of bags after The Grocer 33's latest online survey revealed the retailers put an average of just two or three items in each bag.
The survey found Asda used 15 bags to pack 32 items - worse than in the previous survey three months ago, when it used 14 carriers for 33 products. Sainsbury's, meanwhile, used 11 bags for 33 items - five more carriers than in the previous shop.
Friends of the Earth food campaigner Sandra Bell said she was "appalled" by the numbers of bags. "It seems astonishing that some supermarkets deliver to their customers with an average of only two or three items in each bag. This wasteful use of resources appears to be yet another example of the reality behind the major supermarkets' green claims."
Mike Webster, senior consultant at environmental pressure group Waste Watch, said: "Every year in the UK, more than 17 billion plastic bags are given out by the nine major chains.
"We urge retailers to look again at the alternatives - reusable bags, bags with recycled content or charging customers. For home delivery, cardboard boxes, which can be reused or easily recycled, or reusable plastic crates should be considered."
Webster praised Tesco for offering home deliveries in crates free of plastic bags - an option chosen by our shopper in this week's survey. Waitrose Deliver used just five for 33 items, while Ocado used six for 32 items.
Asda said it was focusing on reducing bag use in home deliveries and on recycling used carriers. "Hopefully this result is not indicative of other deliveries," said a spokesman.
A Sainsbury's spokesman said it made every effort to ensure as few bags as possible were used and it was "disappointing that on this occasion our normal policy wasn't followed".
The Grocer 33 Online p18