Environmentally friendly carrier bags created from the same starch used to make Tapioca pudding are being launched by Sainsbury's.
The new bags decompose 40 times faster
The bags will only be available in three supermarkets, in London and Durham, but the chain hopes to introduce them in other locations if they prove popular.
Shoppers will be encouraged to re-use the biodegradable bags and compost them when they are worn out.
Typical plastic bags can remain in landfills for dozens of years without breaking down, and release harmful chemicals into the earth.
The tapioca bags break down into the common earth elements carbon, oxygen and hydrogen.
Environmentalists have called on the government to introduce a tax on plastic bags to discourage their use.
Such a scheme was launched in Ireland last year and has radically reduced the number of plastic bags littering the streets or being thrown away.
The stores participating in the launch are in Islington, north London, Ladbroke Grove, west London, and Durham.