Supermarkets are today accused by campaigners of charging customers more for plastic-free items. Shoppers save as much as 20 per cent on cans of tuna and tins of baked beans if they bulk buy multipacks of four wrapped in plastic.

Charities today call on the Britain's next Prime Minister to intervene, and said major supermarkets such as Sainsbury's and Tesco to end the "scourge of pointless plastic".

It comes on the back of the Telegraph's new zero-waste campaign that calls on the Government, local councils and private companies to do more to boost the country’s lacklustre recycling rates.

Analysis by this newspaper found that in three of the UK's largest supermarkets, it is significantly less expensive to purchase packs of four own-brand canned items wrapped in plastic than it is to buy four cans separately.

In Tesco, one can of own-brand baked beans is 32 pence, but four wrapped in plastic is just £1. Those buying the multipack save 28 pence - almost the cost of another can of beans.

Similarly, a can of own-brand tuna in brine is 98p whereas a plastic-wrapped selection of four is £3.25, meaning shoppers who choose the plastic version save 67 pence.

In Sainsbury's, one can of own-brand baked beans is 30 pence and four is £1, meaning those who choose the plastic-wrapped multipack save 26p.