Labor ahead in Fisher by-election in SA

The South Australian seat of Fisher could be about to return to the Labor party.

The death of long-serving MP Bob Such in October forced a by-election in the seat south of Adelaide.

With more than half the votes counted, Liberal candidate Heidi Harris is ahead on primary votes but is trailing Labor candidate Nat Cook in the two-party preferred count.

On Sunday the ALP's had a 628 vote lead, a swing of more than nine per cent from the Liberals.

Federal Labor leader Bill Shorten says the Liberal party is suffering because of the federal government.

"The latest advice I have is the swing against the Liberals there is 9.3 per cent," he said.

"There is no doubt when it comes to broken promises, South Australians are feeling very bruised from the death of the car industry through to the government breaking its promises on the Australian Submarine Corp, threatening thousands of jobs.

"There is no doubt in my mind that the Liberals, as they approach Christmas, are suffering because of Tony Abbott and the federal government."

Dr Such was diagnosed with a brain tumour just a week after the last state election and died in October, after holding the seat for 25 years.

He spent 10 years as a Liberal party member before becoming an independent in 2000.

Dr Such won the seat from Labor MP Philip Tyler who held it for just one term.