South Australia's plastic bag ban has pushed Australia to a tipping point and bags should be banned nationwide, supporters say.

South Australia is today becoming the first state to ban lightweight plastic checkout bags.

The ban is expected to reduce the 400 million bags which end up in South Australian dumps every year.

Jon Dee, the founder of the Do Something Campaign to rid the country of the free plastic bag, says today's change is a big breakthrough.

"One of the most interesting things about it is that it's making all the national retailers ban plastic bags," he told ABC Radio National's Breakfast program.

"The argument now is if they can do it in that state there's no reason why they can't do it in every other state."

Labor went to the last federal election pledging to bring in a national ban on plastic bags.

But its plan to phase out their use by the start of this year lost momentum when a meeting of state and federal environment ministers failed to come to an agreement in April last year.

Mr Dee says the South Australian ban could be more effective because it will provide the template for a broader scheme.

"It's disappointing in some ways that South Australia is the only state, however great news that they've actually done it because it has of course been promised nationally for many years now," he said.

"If you look at (Prime Minister) Kevin Rudd and (Environment Minister) Peter Garrett they did promise a national phase-out by the end of last year and that was originally agreed to by all the states.

"When that fell over thankfully South Australia said we're going to go ahead and do it."

He says banning plastic bags has support from shoppers and retailers alike.

"All the research that's been done to date ... is showing it's got incredible levels of support and it's been so well accepted at the retail level.

"If you look at Target for example it's gone so well for them that they've decided to ban plastic bags on a national basis. We're also hearing strong rumours that Target is not the only national retailer considering a similar ban."

Retailers have warned of confusion as the ban takes effect, and the South Australian Retailers' Association says reusing old plastic bags for meat or fish one week and vegetables or fruit the next could have unintended health consequences.

"We leave these things in cars, there's hygiene issues associated with that, so our concern is that there is an opportunity of health issues coming in because of the recalcitrance of the South Australian Government," said executive director Richard Evans.

Under the new arrangements in South Australia shops will have to supply reusable or environmentally friendly alternatives such as cornstarch or paper bags.

Retailers could get an on-the-spot fine of $315, or a maximum penalty of $5,000 if they are caught breaching the ban.

Environmental group Planet Ark is also urging other governments to follow South Australia's example.

The group has launched a petition called Kill of Plastic Bags, Not Wildlife, which will be sent to a meeting of state and federal environment ministers on May 22.