Lidl UK has defended its decision to charge 9p for its “stronger” carrier bags, despite other retailers selling similar products at a lower price.

The discounter will remove single-use 5p bags from sale across all stores in England, Scotland and Wales from next July, leaving its 9p stronger plastic bags as the cheapest option.

But Sainsbury’s, which removed single-use bags from sale last October, sells the stronger alternatives for just 5p. There appears little difference between the recyclable Sainsbury’s bags and those offered by Lidl, but the discounter said its bag was bigger and had a different design.

Sainsbury’s also gives all profits from recyclable bag sales to charity - although, unlike single-use bags, there is no obligation to do so. This has resulted in £2m of donations to date.

Lidl has not confirmed how much of the proceeds from its reusable bags will go to charity, if at all. It is, however, set to raise £1m from single-use carrier bags this year, which will be divided between Keep Britain Tidy and its ongoing charity partner CLIC Sargent. And Lidl pledged to continue supporting charity partners “through other activities”.

The discounter said it had scrapped single-use bags for environmental reasons, and estimates the move will save 63 million plastic bags per year - the equivalent of 760 tonnes of plastic. It has always charged for carrier bags even before the government regulations came into force, which Lidl said reflected a long-held ambition of encouraging shoppers to be more environmentally minded and opt for reusable carrier bags.

“Our pledge to stop selling single-use carrier bags is all about promoting a more environmentally friendly alternative,” said Lidl UK commercial director Ryan McDonnell.

“It will directly encourage shoppers to think about sustainability, and the role they can play in reducing unnecessary plastic waste. We see it as our role to invest in a sustainable future and to bring our customers on that journey with us.”