Supermarkets have been accused of exploiting a loophole by using excessive and unnecessary plastic bags for click and collect and delivery services despite vowing to curb the practice.

Customers of four of the UK’s largest supermarkets have complained that disproportionate numbers of bags are regularly used to pack their shopping, often packing just one item per bag and sometimes even when they have specifically ticked “no bags” at the online checkout.

Environmental charities accused the retailers of failing to take public outrage over “pointless plastic” seriously.

Paul Morozzo, ocean plastic campaigner for Greenpeace UK, said: “Supermarkets claim to be concerned by the plastic tragedy befalling our oceans, and responsive to the outrage from the public.

“But little scandals like this, where they foist pointless plastic packaging on customers who have specifically asked them not to, demonstrate that they’re unlikely to take the problem seriously until they’re paying for it.”

Ever since new legislation was introduced in 2015, large shops have been required to charge 5p for all single-use plastic bags. But Sainsbury’s, Tesco, Asda and Ocado are all accused of delivering goods in carrier bags without charging customers a penny.