One in five Aussie shoppers is opposed to retail giants Woolworths and Coles introducing bans on single-use plastic bags.

While the bans have been welcomed by green groups and many shoppers, research by Canstar Blue shows 20 per cent don’t agree.

Woolies introduces its ban on Wednesday, when its supermarkets, BWS, Metro and petrol outlets will stop offering free disposable bags to shoppers in NSW, Victoria, Queensland and Western Australia.

Coles will follow suit on July 1.

Canstar says more than half of shoppers have already begun stockpiling plastic bags at home, based on a survey of more than 2200 people.

While 71 per cent of those surveyed back the ban, 21 per cent disagree and 8 per cent are undecided.

Nearly half expect that taking their own bags to the shops will be a hassle.

Canstar says many shoppers are stockpiling single-use bags. Photo: AAP

“While the plastic bag ban is supported by most, the supermarkets can expect some frustrated customers in the weeks ahead,” Canstar Blue editor Simon Downes said on Monday.

“While Coles and Woolworths have been trying to get the message across, there will still be lots of shoppers turning up unprepared and shocked that they’ll need to purchase one or more bags to carry their groceries home.”

Some Woolworths shoppers have threatened to boycott the retailer after it revealed plans to charge its online pickup and delivery customers $1 to have their goods packed in reusable bags.

Home delivery customers opting for a new “crate to bench service” will have to fork out $3.50 per order.

Many angry shoppers have taken to the Woolworths Facebook page to criticise the charges.

Stephanie Davey wrote that while she supports the removal of single-use plastic bags, the new extra charges were “completely unreasonable” given she already pays an annual delivery fee.

“I do now need to accumulate heavy duty bags every delivery, and do not want to pay $3.50 to remove my groceries from the crate. I will happily do this myself! Disappointed customer, looking to the opposition who are not charging an additional fee,” she wrote.

So @woolworths you will actually be charging me more to have no bags?!? $3.50 extra to have #nobags 🤦🏼‍♀️ pic.twitter.com/DWkZoWqhht

— Alicia Potts (@AliciaCPotts) June 15, 2018

Greenpeace spokeswoman Zoe Deans said the bans should dramatically reduce plastic waste, particularly on Australia’s coastline.

“It takes a bit of getting used to, and remembering to pop your re-usable bag into your handbag or backpack to make sure you have one on hand,” she said.

“But we do think people understand the pervasiveness of plastic and that it takes hundreds of years to break down in the environment.”

Bans on single-use plastic bags in several European countries since 2003 have led to a 30 per cent drop in plastic bags found in waters off the continent, according to a study published in the journal Science of the Total Environment in April.

-AAP