Australia's outgoing prime minister Malcolm Turnbull said on Friday he would resign from parliament "not before too long" after being ousted in a leadership battle, leaving the government's one-seat majority at risk.

Turnbull's resignation would leave the government of new Prime Minister Scott Morrison facing a by-election for Turnbull's Sydney seat that could see it lose its one-seat majority.

"I'll be leaving the parliament not before too long. As I have always said. I've been very clear about that. It's not a secret," Turnbull told reporters in Canberra.

Treasurer Morrison will become Australia's 30th prime minister after winning a Liberal party leadership vote on Friday, ending an internecine battle that has scarred the conservative government ahead of an election due by May 2019.

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