The former SAS commander today threw up the white flag, announcing his retreat from the race for leader of the opposition.

Mr Hamilton-Smith, who barely survived a Liberal leadership vote last Saturday, won't contest a fresh ballot on Wednesday, but has vowed to stay on as the member for Waite.

He told reporters he would continue to serve the people of South Australia as he always had done.

"I'm not a professional politician and I never pretended to be," he said.

"For two-and-a-half years we've been a united and strong and vibrant opposition until the last few weeks."

Mr Hamilton-Smith called a spill of the leadership last week amid internal party tensions and public speculation over his performance as leader, but decided to hold another ballot after Saturday's vote ended 11-10, with one MP abstaining.

Mr Hamilton-Smith said he could have sailed through on the marginal win, in which he defeated his former deputy Vickie Chapman, but that he was "not that sort of person".

The former childcare centre owner called another vote for Wednesday, seeking a more decisive outcome, but said he would not contest the next ballot.

"I think any other decision than the one I took would have meant more pain," Mr Hamilton-Smith said.

The leader's decision to quit the leadership has opened the door to three contenders - Ms Chapman, current deputy Isobel Redmond and former environment spokesman Mitch Williams.

Ms Redmond, who won the deputy position on Saturday nine votes to five, said that if elected she would "absolutely" want Mr Hamilton-Smith on her front bench.

"It's sad in many ways that someone who has led us as a cohesive team for two-and-a-half years had ended up with the demise of his leadership in this way, but that said, everyone who comes into politics knows ... the landscape changes," she told reporters.