It follows criticism he should have helped the Liberal Party retain the seat he held from 2004 until quitting parliament in August after being replaced as prime minister.
“I am out of partisan politics and so that is it,” the former prime minister told reporters today.
“I will continue to have things to say about important matters of public interest, but I am not engaged in politics any longer. I’m retired.”
Independent MP Kerryn Phelps still appears on track to win the by-election and secure the previously safe Liberal seat, as the government shows no signs of concern about a minority-held parliament.
Turnbull has come under-fire from his former party for not campaigning on behalf of its candidate Dave Sharma.
He had been holidaying in the United States after his resignation sparked the by-election, but returned to Australia on Monday.
Prime Minister Scott Morrison said numerous approaches – including from Sharma himself – for support in the by-election were turned down by Turnbull.
Morrison said the electorate had vented its anger at the government for rolling its long-serving member as prime minister.
Phelps is sitting on just over 51 per cent of the two-candidate preferred vote to Sharma, ahead by 1626 votes.
The Australian Electoral Commission will conduct postal vote counting today.
If, as expected, Phelps wins the seat, she will push the Coalition into minority government.
She will be one of six crossbenchers to the Coalition’s 75 members and Labor’s 69.
Government Senate leader Mathias Cormann told an estimates hearing on Monday the “pure maths” of the lower house would not change.
Cormann said he believed the government had confidence and supply in the lower house, based on public comments made by crossbenchers.
However, if Labor wanted to challenge this, it could always bring on a motion of no confidence.
The federal Opposition would need 76 votes to pass such a motion.
Phelps has yet to have a conversation with Morrison, but has received a text message from him saying “counting was still going on”.
She wants to bring asylum seeker children on Nauru to Australia for treatment and for the government to make a strong commitment to tackling climate change.
Three crossbenchers, Cathy McGowan, Rebekha Sharkie and Bob Katter, want the government to run its full term.
However, Katter told Sky News he had an “untamed unpredictability”.
Independent Andrew Wilkie will not guarantee confidence, while Greens MP Mr Bandt says an election has to be called because “the sooner we turf out this rotten government, the better”.
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