The study’s authors said they recognised a “discrepancy” regarding compostables, between their work and the publicity given to it.

They have now modified the text of their findings, with references to compostable bags eliminated everywhere except in one paragraph.

The conclusions show that compostable plastic bags biodegrade in marine environments and that they degrade in soil.

A spokesperson for Italian compostable bioplastics company Novamont said: “The irony is that no one selling compostable plastic bags ever claimed this. They simply claimed that these bags should be composted. Simple.”