Vote counting in the party ballot was continuing on Sunday, with Mr Swan understood to be leading the postal vote count.

Incumbent president Mark Butler is believed to be lagging Mr Swan, who is polling about 48 per cent of the vote, by at least 12 per cent.

However electronic votes were still to be counted.

Mr Swan is retiring from parliament at the next federal election, while Mr Butler is looking for a new seat after his was slated for abolition in a recent boundary redraw in South Australia.

Mr Swan campaigned on a platform of addressing inequality and boosting party membership.

The party's national conference will be held in December.

Australian Associated Press