The bags, which were introduced as part of a drive by the supermarket to reduce packaging, use 75% less packaging than the standard plastic milk bottle, and now account for one in 10 sales of the two-pint size of milk.
Initially introduced by Sainsbury’s in 2008, the bags were rolled out nationally in February this year and now around 110,000 are sold every week.
Senior dairy buyer Emma Metcalf-King said: “The fact that our customers want to do the right thing for the environment have driven sales way ahead of our expectations.”
The bags are made from strong low-density polyethylene and fit within a reusable jug which contains a spike that pierces the bag, forms a no-leak seal, and delivers milk through the spout. Compared with an equivalent two-pint plastic bottle, milk in a bag costs six pence less.
This news from Sainsbury’s is in contrast to that of Waitrose who recently withdrew sales of their plastic milk bag amid complaints that customers found the product difficult to use.
Metcalf-King insists that educating customers has helped with sales of the milk bags. She said: “Before launch, we gave free jugs to our store colleagues to make sure they understood how to use them. As a result, our colleagues have proven to be the best ambassadors for the product, as they are able to explain it to customers using their own personal experience.”