Barnaby Joyce has blasted former prime minister Malcolm Turnbull for quitting parliament and triggering a by-election, as Liberal candidates begin to jostle for his prized Sydney harbourside seat.

Malcolm Turnbull has told supporters he will quit as the member for Wentworth on Friday.

Business Council executive director Andrew Bragg resigned his post on Tuesday morning to run for preselection in the blue-ribbon seat.

"I thank Jennifer Westacott, the staff and members for the opportunity. Under the party's rules, I am unable to make further comment on the preselection," he posted to social media.

Dave Sharma, Australia's former ambassador to Israel, has also entered the race.

Liberal backbencher Tony Abbott, who orchestrated Mr Turnbull's demise, is endorsing his sister Christine Forster to replace his arch-nemesis.

Ms Forster, a City of Sydney councillor, said she had a strong record of championing Liberal Party values at a local government level.

"I think as someone with local credentials and a strong track record of strong liberalism, I feel they are the types of candidates we want in any seat," she told AAP.

Mr Joyce, a former Nationals leader, served as Mr Turnbull's deputy until being forced to quit after getting a staff member pregnant.

He argued it would have been "more honourable" for Mr Turnbull to serve out his term on the back bench.

"You leave on the right terms with the electorate and the right terms with your nation," Mr Joyce told Seven Network.

"To say 'oh well I'm not the prime minister anymore ho hum, you guys might lose government' - the government that he led - I think people are really disappointed with him about that."

Mr Turnbull comfortably held the blue-ribbon seat of Wentworth with a margin of 17.7 per cent at the 2016 election.

Labor's candidate for the seat, local businessman Tim Murray, has earnt praise from a potentially surprising source - Mr Turnbull's Singapore-based son.

"He's a great guy and I know him well," Alex Turnbull told Fairfax.

Independent Tasmanian MP Andrew Wilkie believes a decent unaligned candidate could snatch the seat.

"It is ripe for a really high-profile independent to pick up the disaffected Liberal voters and also the more progressive voters," Mr Wilkie said.

NSW independent MP Alex Greenwich has confirmed he will not run as an independent in the seat, while GP Kerryn Phelps is still considered a tilt.