Many Australians are still struggling to embrace the plastic bag ban in supermarkets, with one in five often having to buy more bags after forgetting their reusable bags at home.

But about 20 per cent of shoppers – especially 18 to 29-year-olds – have been so resistant to the change that they have admitted to stealing reusable bags to avoid forking out an extra 15 cents a bag, according to research from Canstar Blue.

The survey of 3000 Australians found that just 1 per cent of shoppers did not care about buying new bags for every shop, while 80 per cent quickly changed their behaviour to reuse their bags.

But 20 per cent regularly forget to take previously bought reusable bags when they head out to the shops. More than 40 per cent complained that carrying their bags with them was a hassle.

Coles and Woolworths stopped freely supplying single-use plastic bags at checkouts earlier this year amid mounting pressure to reduce plastic waste.

However, some shoppers were initially outraged by the ban. Coles caved in, continuing to hand out bags weeks after the ban was supposed to have come into effect.

“15 cents for a reusable bag may not seem like much of a cost to pay for doing your bit for the environment, but if you’re buying several bags a week, over the course of a year, those costs add up,” Canstar’s Simon Downes said.

“Many shoppers will now have dozens of reusable bags stored under their kitchen sink, but they still forget to take them shopping, and end up coming home with more.

They’ve gone from throwing away plastic bags to throwing away money.

“Supermarket shopping can also be spontaneous, so you won’t always have your own bags at hand. It’s understandable that some shoppers are frustrated and still struggling to change old habits.”

Older shoppers were the most supportive of the ban with 90 per cent of shoppers aged 60 and over regularly bringing their bags. This is despite earlier concerns that seniors would be the most resistant to the change, and most forgetful.

Instead, it was younger shoppers who rebelled hardest against the inconvenience – only 68 per cent of Australians aged 18 to 29 usually remembered to bring their bags.

The survey found that men were more likely to complain about taking reusable bags or steal replacements from the checkout.

“It seems that plastic bags are being seen as ‘fair game’ by some shoppers who either forget to bring their own bags, or simply don’t think they should have to pay for them,” Mr Downes said.

“But the reality is that, if you take something you need to pay for without paying, it’s stealing, regardless of the cost.”