South Australian police would have shoot-to-kill powers in the event of a terrorist attack if the Liberals won government next year, State Opposition Leader Steven Marshall has said.

The Liberal Party is taking anti-terrorism measures to the March election that it says were inspired by New South Wales legislation put in place after the Lindt Cafe siege of 2014.

Mr Marshall said his plan would give the police commissioner the power to declare an incident a terrorist attack.

"When the commissioner makes such a declaration, it will authorise the use of force, including lethal force that is reasonably necessary to defend innocent people under threat from terrorists," he said.

SA Police are currently restricted from using lethal force against a person unless there is an immediate threat to life.

"This will be changed to allow police to use their weapons to defend people who are threatened by a terrorist or to prevent the unlawful deprivation of liberty," Mr Marshall said.

It followed his announcement on Sunday that the Liberals would order SA Police to audit major public spaces in Adelaide for the likelihood of a terrorist attack and improve safety.

Mr Marshall said it would build on the Federal Government's strategy for protecting crowded spaces from terrorism.

SA Police Minister Peter Malinauskas said there had been no consultation with SA police about the shoot-to-kill powers.

"Mr Marshall seems to be more interested in trying to grab a cheap headline than actually going about the business of working with police," he said.

He added that police already monitored major public events.

"Steven Marshall has decided to come out and announce a policy which is essentially a replication of everything that we already do when it comes to event management and security in South Australia," Mr Malinauskas said.

"We're very fortunate that SAPOL already work very closely with all major events that occur in South Australia to ensure the security and safety of patrons that attend those events."

University of Adelaide associate lecturer David Olney said security had already been boosted at public venues.

"It's a good idea but a good idea that probably can't be funded or organised with the limited resources we have in a small state," he said.

"We can only do so much."