The head of the Joint Research Unit: “Agropolymers Engineering and Emerging Technologies” in Montpellier, France, also questioned the environmental credentials of certain green packaging materials.

Some so-called biodegradable or compostable plastics are not actually biodegradable in the soil and require specialist treatment that is not widely available. If these materials are not being treated correctly, it makes little sense to use them in the first place.

Guilbert also said telling consumers that packaging is now biodegradable could have perverse consequences. People may take less care to dispose of used packaging, creating littering problems.

These question marks over the environmental and ethical value of green packaging materials led Guilbert to conclude that they should only be used when there is a functional justification and she said that many bio-plastics are inferior to conventional materials on all levels.