The new South Australian government has been warned Labor could use its numbers in the upper house to block legislation to deregulate shop trading hours.
Former treasurer Tom Koutsantonis says new Premier Steven Marshall had set "a very, very dangerous precedent" when he blocked the former Weatherill government's state banking tax in last year's budget.
"I think when leaders of the opposition have rushes of blood to their head and make decisions overturning decades of precedent in this state, I think there will be consequences for it," Mr Koutsantonis told ABC radio in Adelaide on Monday.
Had it passed, the banking tax would have imposed a $370 million levy on major banks in the state.
Mr Marshall was criticised for his opposition to the tax despite the huge annual profits of the big banks, but he said it was a bad tax.
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"It was not going to help South Australia, in fact it was going to hurt South Australia and we had no choice."
Mr Marshall said the tax would have hurt business, but Labor could not use the same argument in their opposition to deregulation of trading hours.
"It's hard for Labor to argue that they need to block deregulation of shop trading hours because it would be bad for South Australia," he said.
"If they honestly believe that then why don't they regulate all the shop trading hours in country SA?"
He said deregulation legislation, which is included in the Liberals' plan for their first 100 days in office, will be introduced as soon as parliament is recalled.
Josh Peak, assistant secretary for the retail, fast food and warehousing union, said deregulation gives big business more power and the upper house has no obligation to pass the legislation.
"Governments don't have the opportunity just to push through bad policy - that's why we have an upper house in the first place," he said.
