Woolworths has begun a trial of paper bags in select stores, a move environment groups say is preferable to the use of plastic though the focus should remain on reusable bags.

The paper bags cost 20c each and are currently available in 20 stores around the country, and will be offered in addition to the existing reusable thick plastic bags that cost 15c.

On Friday, a Woolworths spokeswoman said “the vast majority” of customers brought their own bags but when shoppers forget, “some customers have told us they would like the option of a paper bag”.

The bags are made of 80% recycled paper and the supermarket chain say they will monitor customer demand in the coming weeks.

Both Woolworths and Coles banned single-use plastic bags in July last year. Instead of handing out free bags, made of thinner plastic, the chains only offered thicker, reusable plastic bags at a cost.

In December, the National Retail Association estimated the decision has led to an 80% drop in plastic consumption. Woolworths has estimated that the ban has stopped more than 3 billion bags entering circulation.

Jeff Angel, the director of environmental groups such as the Total Environment Centre and Boomerang Alliance, welcomed the move but said the focus should stay on reusable bags.

“Paper bags are better than plastic because the material is sourced from renewable plantations and are compostable; unlike plastic, along with its poisonous pollution of the ocean.

“However the main focus must continue to be genuinely reusable bags as many of the thicker 15c plastic bags are only used once. Hopefully more and more people will remember to bring them when shopping.”

In August, Coles triggered confusion by announcing it would provide the new bags for free for an indefinite period to let shoppers adjust. The chain then reversed this decision after criticism from environmental groups.

In New South Wales, the bags will be available at the Rouse Hill, Marrickville Metro, Town Hall, Neutral Bay, Double Bay, Bondi, Rozelle, Coogee, Paddington and Rose Bay stores in Sydney.

In Victoria, they are at the South Yarra, Armadale, Black Rock, Hawksburn, St Kilda, Hawthorn and QV Melbourne stores in Melbourne.

In Queensland, they are available in the Cairns, Surfers Paradise and Pacific Fair stores.