Experts have criticised Morrisons’ decision to switch from plastic to paper bags for fruit and vegetables, branding it a retrograde step for efforts to tackle climate change.

This week the supermarket ditched transparent plastic bags in favour of recyclable paper ones, in a move it said was prompted by customers’ worries over pollution. But the step is likely to have unintended consequences and trade one environmental challenge for another.

The Environment Agency found that paper carrier bags, across their lifecycle of production, use and disposal, had a greater global-warming impact than plastic ones. The agency’s study found paper ones were only better than plastic if they were used four or more times, but that was unlikely due to durability of paper bags.

While the research was published seven years ago, the government’s top waste and recycling advisers, Wrap, said the findings were still relevant today.

Chris Goodall, an author and environmental expert, said: “This is a retrograde step, moving back to paper.”

He agreed the impact of plastic pollution on marine life was very serious, but said: “Most of the plastic in the sea comes from a small number of rivers, it does not come from me buying green beans in Morrisons.”

Compared to using plastic bags for loose fruit and vegetable, paper bags were a backwards step in climate and energy use terms, Goodall said. One reason for the greater climate impact is that using paper will lessen the life expectancy of produce, he argued, leading to more food waste in landfill, where it generates methane, a powerful greenhouse gas.

Quick Guide Plastics and our throwaway society Show Why is plastic being demonised? Since the 1950s, 8.3bn tonnes of plastic has been produced. Plastic is seen as a versatile, indispensable product, but the environmental impact is becoming more stark. Plastic is now so pervasive that recycling systems cannot keep up and the leakage into the environment is such that by 2050 plastic in the ocean will outweigh fish. In 2017 scientists found plastic fibres in tap water, and plastic has been found in the stomachs of sea creatures in the deepest part of the ocean. Most plastic waste ends up in landfill sites or leaks into the natural environment, where it is causing huge damage to eco-systems on land and sea, creating near permanent contamination. According to academics in the United States, by 2015, of all the plastic waste generated since the 1950s, only 9% has been recycled, with 12% incinerated and 79% accumulated in landfill sites or the environment. Why are the supermarkets under fire? Producers of plastic include retailers, drinks companies and supermarkets. Supermarkets create more than half of the plastic waste in the household stream in the UK. But they refuse to reveal how much they put on to the streets and how much they pay towards recycling it. Supermarkets are under pressure to reduce their plastic packaging and campaigners argue they have the power to turn off the tap. Much of the packaging they sell to consumers is not recyclable: plastic film, black plastic trays, sleeves on drinks bottles and some coloured plastic. The Recycling Association and other experts believe supermarkets could do much more to make packaging 100% recyclable and reduce the use of plastic. Who pays to clean up the waste? The taxpayer, overwhelmingly. UK producers and retailers pay among the lowest towards recycling and dealing with their waste in Europe. In other countries, the “polluter” is forced to pay much more. In France, a sliding system of charges means those who put more non- recyclable material on the market pay more. What can shoppers do to help? Supermarkets are under pressure, not least from the prime minister, to create plastic-free aisles. A growing number of zero-waste shops are springing up and consumers are being encouraged to ask for products to be sold without plastic. Sandra Laville Photograph: ermingut/E+

However, Friends of the Earth said that it welcomed Morrisons’ switch and that green issues other than climate change should be factored in.

Julian Kirby, a campaigner at the group, said: “The thing about climate change is because it’s such a huge worry it has eclipsed other very serious environmental and health concerns, and that would include … pollution.

“With a paper bag, if it escapes into the environment it will biodegrade very soon. That is not the case with a plastic one.”

The supermarket appeared aware of the trade-off, saying it had weighed the environmental impact of paper against the potential pollution from plastic.

“We have listened to customers and they are telling us that the overuse of plastic is the most important environmental issue for us to deal with,” a spokesperson said.