Consumer pressure to end plastic packaging in shops could actually be harming the environment, a report says.
Firms are swapping to other packaging materials which are potentially even worse for the environment, the cross-party Parliamentary group warns.
Glass bottles, for instance, are much heavier than plastic so are far more polluting to transport.
Paper bags tend to have higher carbon emissions than plastic bags – and are more difficult to re-use.
The change in packaging materials has been prompted by concern from shoppers about the impact of plastic waste in the oceans.
But the authors of the report, called Plastic Promises, say the consequences of using new materials have not been properly assessed.
Several supermarkets, for instance, are selling more drinks in coated cartons under the assumption that they can be recycled.
In fact, the Green Alliance says, the UK only has the facilities to recycle a third of the coated containers in circulation.
The group has been working with recycling organisations to survey shops’ anonymous responses to public anxiety about plastic polluting the oceans.
Its spokeswoman, Libby Peake, told BBC News: “A lot of shops are selling packaging described as biodegradable or compostable.
“In fact the items might only be composted in an industrial composter – and, even then, some items might not be fully digested.”
The report says: “Over 80% of consumers think biodegradable or compostable plastic is environmentally friendly, but there is little understanding of what the terms mean and how the material should be dealt with.
“Our interviewees wanted a clearer approach to where it should be used and how it should be marked to avoid confusing consumers and potentially causing more problems.”
The retailers worried that confusion could potentially harm the environment if people either put “compostable” plastic in with conventional plastic, or littered it, wrongly assuming it would biodegrade like an apple core.