The retailer said the tray is home compostable: “Once put outside on the compost heap the Plantic tray will take around three weeks to totally breakdown. The tray can also be put under water in which it will dissolve in a matter of minutes.”

Plantic biopolymer film is starch-based and compostable to EN 13432 standards.

M&S said it was the first UK retailer to trial plantic back in 2007, and after successful customer feedback it has now decided to use the material for this confectionery range. "This will be the widest range of products available on the high street packed in Plantic," added the company.

As part of its environmental sustainability strategy, Plan A, the retailing giant claims it is committed to increasing the amount of packaging it uses that is made from sustainable raw materials.

Its head of packaging, Helene Roberts commented: “We want to make sure the packaging we use can be easily recycled or composted."

The only material not compostable in its Swiss chocolate range, said the group, will be the plastic film wrapped around the chocolate box: “This is made from PP, [which] is recyclable but is not currently collected in the UK,” added the retailer.

Meanwhile, a recently signed deal between Australian company Plantic Technologies and Klöckner Pentaplast Group will see the distribution of Plantic film in Europe and the Americas.

The biopolymer, said the developer, is suitable for chocolate as well as other types of confectionery and other applications such as biscuits.