Usually costing 10p each, Sainsbury's hopes that giving people its 'bags for life' will encourage customers to keep and reuse the bags for future shopping trips.
"Our customers are showing an increasing interest in wanting to be greener or healthier, but tell us they would like more information and help on what they can do and ideas on specific positive steps they can take," said Sainsbury's customer director Gwyn Burr.
"That's why Sainsbury's is launching 'make the difference' days to champion specific issues to help and encourage customers and colleagues to take simple steps and actions to effect real change. Working in partnership is the key. On the first day we will provide the bags for free but need customers to reuse them to really make the difference," she continued.
"Working together these small and easy changes today can make real and lasting differences for tomorrow."
Sainsbury's says that more than 90 million disposable plastic bags could be saved it customers used the more environmentally-friendly equivalent at least 20 times.
And the supermarket expects to hand out seven million of the reusable bags on April 27th alone; a figure it would normally take two years to reach.
"Too many of us rely on free carrier bags when we shop and as a result 13 billion of them are used up every year in the UK, "commented Dr Liz Goodwin, chief executive of the Waste and Resources Action Programme (Wrap).
"From our research we know that it's very difficult for shoppers to adopt greener habits without support, and Sainsbury's is clearly trying to encourage customers to re-use bags in a very positive way."
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