Alexander Downer.

Alexander Downer. Photo: Peter Braig

Former federal Liberal leader Alexander Downer said he had ''no plans'' to seek the leadership of the South Australian opposition after the resignation of leader Isobel Redmond.

Amid ongoing speculation that Mr Downer was ready to take over, Ms Redmond issued a statement on Thursday citing the leadership rumours and disunity for her decision.

''I have been privileged to lead the state Liberal parliamentary (side) for the past three and a half years,'' she said.

Isobel Redmond on the campaign trail.

Isobel Redmond on the campaign trail. Photo: David Mariuz

''However, in the face of ongoing leadership speculation and disunity I have reached the conclusion that it is in the best interests of the Liberal Party if I step aside.

''Whoever is chosen as the new leader has my guarantee of my loyalty and support.''

She said she would work ''conscientiously'' as the member for Heysen and do everything to ensure a Liberal win at the election in March 2014.

Mr Downer, who was Australia's longest serving foreign minister, has said previously he was not intending to return to politics but has resisted ruling it out entirely.

Outside the National Press Club in Canberra on Thursday, Mr Downer said he had no plans to seek the leadership.

''I'm not a member of the state parliament, I don't have any plans to enter the state parliament and the new leader will presumably be elected and she or he will have my support,'' he said.

Mr Downer, who has previously said his wife opposed any return to politics, said: ''If I was about to change my plans that would be part of my narrative.''

SA Premier Jay Weatherill said in a statement that Ms Redmond had been forced to resign due to treachery within the Liberal Party, which he said she had ''bravely'' tried to withstand.

''This is the culmination of the most treacherous and deceitful undermining of a leader we have seen in this state,'' he said.

Should Mr Downer put his hand up, win the leadership and become premier, he would be following his grandfather, Sir John Downer, twice a South Australian premier and also a member of the first federal parliament in 1901.

Mr Downer was foreign minister from March 1996 to December 2007 after an unsuccessful stint as opposition leader from 1994 to 1995, the shortest-serving of any Liberal leader.

He is also, with Brendan Nelson and Malcolm Turnbull, one of three federal Liberal leaders never to lead the party into an election.

After enjoying early support among voters, Downer's support base was quickly eroded by a series of embarrassing public blunders, including joking at a formal dinner that the party's slogan "The Things That Matter" should be named "The Things That Batter" for its domestic violence policy.

He resigned from parliament in 2008 and is currently UN special adviser to the Secretary-General on Cyprus.

A ballot will be held for the leadership on Monday at 9am.

with staff reporters and AAP

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