Former Opposition leader Martin Hamilton-Smith is to challenge the woman who replaced him, Isobel Redmond, in a spill for the Liberals' South Australian leadership.

There is to be a meeting of state Liberal MPs next Tuesday morning in Adelaide.

Current deputy Mitch Williams will be challenged for his job by shadow frontbencher Steven Marshall.

Liberal Party whip Steven Griffiths said the required number in the party had supported the spill motion.

"I've received a letter this morning signed by the required number of members of parliament requesting a meeting to be convened on Tuesday of next week on the position of leadership," he said.

Despite a recent opinion poll giving the Liberals an election-winning lead over the Labor Government in SA, Ms Redmond has been under pressure for her performance.

Hamilton-Smith, Marshall statement On Tuesday 23rd October the positions of leader and deputy leader of the State Parliamentary Liberal Party will be declared vacant and a ballot will be held. At the request of colleagues, we intend to nominate together for the positions of leader (Martin Hamilton-Smith MP) and deputy leader (Steven Marshall MP). The Liberal leadership and deputy leadership is a matter for the state Parliamentary Liberal Party. We will be speaking with each of our colleagues between now and Tuesday regarding this matter. In the event that we are successful we will hold a press conference following the ballot outlining our plan to deliver growth, vitality and prosperity for all South Australians.

The issue flared again after her recent comments about wanting big public sector job cuts, comments she swiftly retracted.

Ms Redmond conceded the party had not discussed or formed such a policy.

There has been talk of former federal Liberal Alexander Downer being drafted into SA politics to take the leadership, but Mr Downer has played down any such suggestion.

He said he had no plan to do so and his wife, Nicky, was opposed to him making any political return.

Ms Redmond also was linked with a possible move to federal politics, when Mary Jo Fisher vacated her Senate seat recently.

Isobel Redmond, with Martin Hamilton-Smith (rear) to challenge ( Patrick Rocca: ABC News )

But that vacancy ultimately was filled by a Riverland business operator Anne Ruston.

Ms Redmond entered politics in 2002 and became Opposition Leader in 2009, leading the Liberals to the 2010 poll.

The Liberals stayed in opposition even though they secured more of the two-party preferred vote than Labor.

Mr Hamilton-Smith and Mr Marshall issued a joint statement saying they would stand at the request of colleagues.

But Mr Hamilton-Smith had less to say when he spoke with an ABC reporter in Adelaide.

"The only comment I'm providing is that it's a matter for the partyroom, it will be decided next Tuesday, it's best left to discussions with colleagues and that's all I have to say," he said.

SA Premier Jay Weatherill said Ms Redmond was paying the price for saying 20,000 public servants should be sacked, but he did not care who led the Liberal Party.

He said the Opposition could turn back time or stick with a leader who was being undermined.

"It doesn't really matter, I mean the choice is really for them this - to turn back to a failed leader or to stay with a leader who is being traitorously undermined on a day-to-day basis," the Premier said.

"I don't think it really matters too much, what really matters is a cogent plan for South Australia's future."