The ACT's environment commissioner has recommended a minimum price for plastic bags, as plastic use creeps back to pre-ban levels.
The capital's plastic bag ban has stopped 1132 tonnes of plastic going in landfill since 2011, Commissioner for Sustainability and the Environment Professor Kate Auty found in her long-awaited review of the policy.
This year alone, the ban has stopped 55 million bags ending up in landfill.
However, Professor Auty warned that if the ban is left as is, plastic consumption will return to pre-2011 levels.
Canberrans used about 953 tonnes in 2017-18, compared to 973 tonnes in 2010-11. By the early 2020s, consumption is likely to pass pre-ban levels unless further policy measures are introduced, she said.
"If we do nothing or just keep going as business as usual, we will in fact be back to where we started in 2020-21."
She urged the government to consider a mandatory minimum price on bags based on their weight, at 2 cents per gram.
That could double the price of a reusable cloth bag from $1 to $1.98, and push up the cost of a reusable plastic bag from about 10 cent to 28 cents.
Professor Auty said that could push up the average household's yearly spending on bags by $63 in 2018-19 and $75 in 2024-25.
She said it was the least popular of all the options presented to Canberrans in a recent survey and could face strong opposition, but would provide a consistent incentive to reduce plastic bag use.
“We thought long and hard about whether there was need to be just simply banning plastics and in surveying the public took the view that was not the right thing to do at this time. The minimum price is the way we think to nudge change," Professor Auty said.
The bag ban has already come at a cost to consumers.
Based on plastic bag usage data, Professor Auty estimated shoppers paid $696,000 for bags in 2017-18, or about $4.20 a household per year.
This analysis suggests most of this increase (84 per cent) came down to an increased spend on reusable plastic bags and garbage bags, rather than boutique or green bags.
Despite this, a Reachtel survey suggested the level of public support for the ban had increased over time, from 58 per cent in 2012, 65 per cent in 2014 and 68 per cent in 2018.
Judy McMillan is one such enthusiastic user. She has a special shelf by her front door for her reusable shopping bags and an "emergency" stash in the boot of her car.
"I was more than happy to embrace the non-plastic bag life. I make sure I take reusable ones everywhere, just in case," Ms McMillan said.
"It was funny how, compared to Sydney and Melbourne shoppers, Canberra seemed to deal with the new rules with ease."
Professor Auty also recommended the government introduce a mandatory disclosure scheme, where retailers who sell bags need to report annually on how many bags they've sold.
This data could be collated by the ACT government and reported on a freely available public website, she said.
“It’s critical in my view. We want full disclosure of those elements that underpin the economy of the plastic bag," Professor Auty said.
However, retailers are likely to oppose a mandatory disclosure scheme, on the grounds of commercial-in-confidence.
Professor Auty said while it would be less effective, even territory-wide or electoral division data on plastic bags would be better than nothing.
Sustainability minister Shane Rattenbury said Professor Auty's report sent a clear message the ACT had to take further steps to reduce plastic usage.
"It’s been very successful so far but we cannot rest on our laurels," Mr Rattenbury said.
While Mr Rattenbury commissioned the report last year, he is no longer responsible plastic bag ban after the recent ministerial reshuffle.
Instead new city services minister Chris Steel will be responsible for responding to the report.
"I welcome the commissioner’s report, we will consider her recommendations the government will provide a response within the prescribed timeframe of six months," he said.