Independent South Australian MP John Darley has raised concerns about women's safety if the state's shop trading hours are relaxed.

Key points: Shop trading hours deregulation set to be voted on in SA Parliament tomorrow

Shop trading hours deregulation set to be voted on in SA Parliament tomorrow MLCs John Darley and Tammy Franks say it will put female retail workers in danger

MLCs John Darley and Tammy Franks say it will put female retail workers in danger Government says it hasn't been an issue interstate

Parliament's Upper House is debating the State Government's proposal to deregulate trading hours, which Labor and the crossbench are set to combine to defeat in a vote on Thursday.

While the Government argues deregulation will provide freedom of choice to consumers, traders and workers, Mr Darley says the move will harm the community.

He said the issue was raised by South Australia Police in a submission to the 1977 Royal Commission into the Law Relating to Shop Trading Hours.

"We already have a problem where many, I would say most, women feel unsafe walking alone at night," Mr Darley told Parliament on Tuesday night.

"If these women are then rostered on to work a graveyard shift, I have genuine concern about their safety, if they finish in the middle of the night."

Independent Upper House MP John Darley opposes deregulation. ( ABC: Angus Llewellyn )

He said he was concerned about women walking to and from work on graveyard shifts, because public transport was not up to scratch.

"We simply do not have the population to support this," he said.

"How will the safety of workers going home at odd hours be ensured it we move to a 24/7 economy?"

Deregulating shopping hours was a key Liberal Party promise at the March state election, while the Labor Party — with support from the Shop Distributive and Allied Employees' Association — opposed the idea.

Treasurer Rob Lucas said Mr Darley's concerns were outdated and irrelevant to the debate, and it was in the interest of shop owners to make their premises safe.

"The sort of trading hours we're looking at in South Australia were implemented or instituted in virtually all other states and territories in Australia without any of the sorts of concerns that have been flagged," he said.

"If you're going to have a shopping centre open to nine o'clock at night or whatever it might happen to be, clearly there's a requirement on shopping centre owners and operators to have well-lit premises and surrounds where the carparking might happen to be, so that's common sense in terms of the operation of the business."

Legislation expected to be defeated

The Greens and SA Best are set to join Labor in voting down the measure in the Legislative Council on Thursday.

Greens MLC Tammy Franks said Mr Darley was correct that later shopping hours could put young and female workers at risk.

She said it was also a concern for nurses around North Adelaide's Women's and Children's Hospital.

"Why would you think it would be any different with shop staff?" she said.

"Young women still walk through dark streets at night holding a car or a house key thinking they're going to be attacked."

However, she said her main concern with the legislation was the effect on independent retailers.

Business groups apart from independent supermarkets support deregulated shopping hours. ( ABC News: Eugene Boisvert )

Restrictions at night, Sunday mornings and public holidays

Supermarkets over 400 square metres and other shops over 200 square metres — apart from hardware stores and furniture shops — in suburban Adelaide cannot open at night on weekends, before 11:00am on Sundays or at all on public holidays.

Shops in the CBD and Glenelg can open between 11:00am and 5:00pm on public holidays.

Hours are deregulated in the country, apart from in Millicent and a couple of smaller towns, where supermarkets over 400 square metres cannot open on Sundays or public holidays.

The Opposition says start-ups and small businesses will be harmed if the Government succeeds in deregulating shop trading hours.

Labor MLC Kyam Maher said the independent supermarket in Millicent had been able to support small producers because of the town's uniquely restricted trading hours.

"The independent retailers had helped them with their product development, with packaging, with marketing advice, and with store placement," Mr Maher said.

"In effect, the independent retailers had helped this company become a success."

SA Best MLC Frank Pangallo said Millicent's uniquely restricted trading hours could be lost if the bill were to pass.

"Millicent locals, like people living in other regional communities, are acutely aware of the severe impact any changes to shop trading hours will have in their region, including the potential forced closure of small, family-run businesses," he said.

Mr Lucas said no one in Millicent would be forced to go shopping at night or on Sunday mornings.

"Shops in that particular community won't have to operate, and if people don't want to go to shops that do open, they don't have to support them," he said.