Former Liberal premiers John Olsen and Dean Brown back Steven Marshall

TWO former premiers who were central figures in the factional warfare that tore apart the Liberal Party in the 1990s have backed Steven Marshall.

TWO former premiers who were central figures in the factional warfare that tore apart the Liberal Party in the 1990s have called on state MPs to back South Australian Opposition leader-in-waiting Steven Marshall.

In a public show of support for the man set to become Liberal leader on Monday, Dean Brown and John Olsen told The Advertiser  the party must dedicate itself to removing Labor from office.

Mr Olsen took the leadership from Mr Brown in 1996 and many observers have pointed to their personal rivalry as the rocky foundation on which the Liberal Party's instability of the past decade is built.

Mr Olsen said the state's current debt position had echoes of the State Bank disaster left by Labor in 1993.

"The future is in the hands of the parliamentary Liberal Party," Mr Olsen said.

"With the leadership change about to take place on Monday, hopefully we will see a consolidation and focus on the next election.

"The set of circumstances emerging post the 2014 election are not dissimilar to the set of circumstances that both of us had to persevere with back some time ago."

Mr Brown said internal Liberal squabbling must be consigned to the past.

"The performance of where they go from here as a party is really in the hands of the members of Parliament," he said. "It's crucial to give the support and authority for Steven to do what he needs to."

Former foreign affairs minister Alexander Downer, long speculated as a possible state Liberal leader, yesterday would not comment.

However, Mr Marshall says he has been assured there will be no later challenge.

Mr Olsen's appearance beside Mr Marshall is significant. He's reportedly been a backer of the Downer option.

However, the surface display of Liberal unity will be tested over the weekend and on Monday as squabbling breaks out over the soon-to-be-vacant deputy position. A critical frontbench reshuffle also looms.

Mr Marshall confirmed yesterday morning he would stand for the leader's position on Monday. Senior Liberals say he has cross-factional support and will be elected unopposed.

Mr Downer has United Nations commitments in Cyprus until late next month.

Senior Liberals say former Opposition Leader Isobel Redmond, who quit the post on Thursday, offered to stand aside for him in September. However, Mr Marshall is now expected to get a clear run.

While it is possible Mr Downer could be drafted at a later date, senior Liberals say it is highly improbable.

Mr Marshall yesterday told The Advertiser he would place "getting our economy going again" at the centre of the Liberals' election pitch, if he is appointed leader.

"That's going to inadvertently raise more taxes without sticking up the tax rate," he said.

Mr Marshall denied the likely contest for deputy between water spokeswoman Vickie Chapman and backbencher Martin Hamilton-Smith undermined his call for unity.

Mr Marshall said there would be no reshuffle on Monday if he is made leader but tipped one next week.

Sitting of State Parliament resumes on Tuesday, the first time in 2013.