Turnbull Support 'Out Of The Blue': Phelps

The Liberal Party's biggest threat in Wentworth, Kerryn Phelps, says last-minute support from the son of former prime minister Malcolm Turnbull has come "out of the blue".

Dr Phelps, who is the favourite to win Saturday's by-election according to leaked Liberal polling, welcomed Alex Turnbull's support on Wednesday.

"It's entirely out of the blue," Phelps told AAP.

Alex Turnbull, who's been a vocal critic of the Liberal Party since his father was rolled as leader in August, is now urging Wentworth voters to support the leading independent candidate.

Alex Turnbull.

"Realistically if it's tight, and the preference flows are as they are, it's better to vote for @drkerrynphelps if you want greater certainty of the Liberals not retaining the seat," he tweeted.

"And if you vote for (Labor's Tim Murray) be very sharp about your preferencing."

Internal Liberal polling, published in The Australian, suggests Phelps could secure 55 per cent of the two-party-preferred vote.

The former Australian Medical Association boss says the polling is heartening but must be kept in perspective.

Independent candidate for Wentworth Kerryn Phelps poses after a press conference at Rushcutters Bay in Sydney, Tuesday, October 2, 2018. (AAP Image/Mick Tsikas) NO ARCHIVING

"It's Liberal Party polling so I think you have to take it with a grain of salt but certainly the mood, the feeling in the community, is that they're ready for change and that there is a certain momentum," Phelps said.

READ MORE: Kerryn Phelps On Peter Dutton, Being 'Sensible', And Chocolate

READ MORE: 'Held At Gunpoint': Alex Turnbull Dishes On 'Weird' Liberal Party Politics

Many voters are irate over Canberra's "thought bubble" to move the Australian embassy in Israel from Tel Aviv to Jerusalem in the throes of a by-election campaign, she said.

"People are still annoyed and they're very upset about the chaos in the Liberal Party at the moment."

Phelps has said she'll seek an urgent briefing from Australian security agencies to understand how and why the government floated the idea if she wins on Saturday.

She's not ruled out supporting the move.

Sharma, a former ambassador to Israel, says Mr Morrison's announcement - which would see Australia follow the United States which has already moved its embassy - has nothing to do with Saturday's by-election.

Liberal Wentworth Candidate Dave Sharma.

Meanwhile, polling commissioned by Greenpeace Australia indicates climate change remains the biggest issue for voters in Wentworth.

More than 40 percent of voters surveyed in the ReachTEL poll said climate change was their number one issue.