A compulsory charge on plastic bags at supermarkets has been ruled out despite overseas evidence that a small fee can cut their use dramatically.

Plastic bag use has reportedly dropped by as much as 90 per cent in Wales in the six months since a law change introduced a mandatory 5 pence charge on every bag, with the proceeds going to charity.

Other parts of the United Kingdom look set to follow and the European Union is considering a total ban on plastic bags. In Australia, three states or territories have already banned plastic bags outright.

Similar moves in New Zealand look unlikely, despite the Government indicating in 2009 that it would consider a compulsory charge.

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A spokesman for Environment Minister Amy Adams said today the Government did not consider it practical to introduce a charge at this time.

"Instead, we encourage waste minimisation through voluntary schemes and by educating and encouraging industry and the public to take responsibility for their own waste."

Retailers were using a number of ways to reduce the environmental impact of plastic bags, the spokesman said.

"Many shops now sell or use reusable bags or charge for plastic bags. There are also different types of plastic bags being used, some of which can be recycled."

Plastic bags can take hundreds of years to break down in landfills but are generally used for no more than 20 minutes, although most get re-used at home, according to research.

Green Party waste spokeswoman Denise Roche said she would like to see plastic bags phased out entirely but legislative change was not a priority at the moment.

"You'll find that most supermarkets are now actually offering reusable bags, which is great, but definitely it's not fast enough."

Plastic bags were "a crazy idea", she said.

"You're using a finite resource to basically produce something that becomes totally disposable. We'd like to see them phased out because they're a complete waste."

Wanaka Wastebusters project manager Sophie Ward, who worked on a 2009 campaign to get supermarkets to charge for plastic bags, said there was definitely a case for compulsory surcharges.

"It's amazing to see what a small financial incentive actually does," she said.

Foodstuffs introduced a 5-cent charge on plastic bags at its New World and Four Square stores over four weeks in 2009, resulting in 12 million fewer bags being used - a 60 per cent drop.

But after a public backlash against the move, the company quickly dropped the charge.

Ms Ward said the the only way to introduce a voluntary surcharge was if the two big supermarket chains - Progressive and Foodstuffs - acted together.

"That would make the biggest impact, whether or not they need it to come from government legislation or if they could both agree to do it. But I'm not sure that's going to happen in the short term."

Ms Ward said people would take a little bit of time to get used to charges but they would quickly adapt.

"All of a sudden they're just taking their own bags and it's not that difficult at all to see that changing."

A Foodstuffs spokeswoman said the company was committed to reducing plastic bag use across its stores nationwide.

The company's Pak'nSave stores no longer offered free plastic bags and charged 5c per bag.

"Moving forward we will continue to encourage customers to reduce the number of bags they use. We will do this by promoting reusable bags and continually training our check out staff to pack customers groceries in such a way to ensure minimum plastic bag usage."

Foodstuffs had also been involved in a number of industry-led initiatives designed to reduce the impact of bags on the environment.

Both Foodstuffs and Progressive signed a Packaging Accord in 2004, which by 2009 had reduced plastic bag use by 22 per cent, or 157 million bags.

The Warehouse, which charges 10c per plastic bag, has seen the number of plastic bags people use drop from more than 27 million to almost 7 million - a 75 per cent reduction.

The company's latest community and environment report said there were fewer sales of reusable bags, which showed maturity in the market.

It planned to survey customers and review how it incentivised its waste reduction initiative.

Progressive did not respond to a request for comment.