Labor appears set to be returned for a third term in government, but Premier Mike Rann has so far refrained from claiming victory. Liberal leader Isobel Redmond is refusing to concede defeat but admits her party faces an uphill battle to topple Labor.

Labor is forecast to win 25 seats to the Liberals' 18, with four independents, in the 47-seat lower house.

Mr Rann said it would be presumptuous to claim victory in a state election he described as a kick in the pants for his Labor Party. Labor suffered about an 8 per cent swing against it in Saturday's poll.

However, Mr Rann's likely successor has already made his intentions known. Jay Weatherill, environment minister under Mr Rann, said yesterday he would challenge Kevin Foley for Labor's deputy leader position.

Mr Weatherill, 46, has long been considered a potential leader and said Labor's election plunge meant a fresh approach was needed.

Attorney-General Michael Atkinson said yesterday he would not seek a cabinet position in a re-elected Rann Government because Labor needed renewal.

Mr Rann described Mr Weatherill's challenge as "somewhat premature", saying he would support Mr Foley to continue as deputy leader.

"Jay has got plenty of time; he's got time on this side," Mr Rann said.

He said the swing against Labor, which entered the poll with a 10-seat buffer, was inevitable, but it also sent a clear message.

"What we have seen is a natural correction plus a kick in the pants," he said. "We have got a message from the public, in a number of seats we got a real hiding.

"And we have got to listen to that message from the public and learn from it, take our punishment."

Ms Redmond, meanwhile, said her position as Liberal leader was secure regardless of the final election result.

"I don't think that anyone in the Liberal Party would even think of changing leaders," she told reporters yesterday.