Former Deputy Prime Minister Anthony Albanese will run for opposition leader, a Labor MP has told the Sydney Morning Herald.
He will likely be pitted against Victorian MP and union heavyweight Bill Shorten, who is believed to have greater support within the Labor caucus.
But Mr Albanese, who represents the Sydney inner-west seat of Grayndler, is considered more popular with party members overall.
Under new rules made by Kevin Rudd when he became prime minister for the second time, sitting ALP members of parliament will have 50 percent of the vote in determining who leads the party.
The other 50 percent of the vote comes from party members as a whole.
Mr Shorten is a part of the Victorian Right faction, while Mr Albanese is a major player in the NSW Left.