Christine Forster, the sister of former prime minister Tony Abbott, has confirmed she will nominate for pre-selection in the prize Sydney electorate of Wentworth.

Key points: There could be a by-election at Wentworth, depending on the timing of Malcolm Turnbull's resignation

There could be a by-election at Wentworth, depending on the timing of Malcolm Turnbull's resignation It is a safe Liberal seat, taking in affluent suburbs like Paddington, Point Piper and Bondi

It is a safe Liberal seat, taking in affluent suburbs like Paddington, Point Piper and Bondi The Greens have already named their candidate

Ms Forster, a Liberal councillor for the City of Sydney for the past six years, is one of several high-profile potential candidates who are circling the federal seat, which is yet to be vacated by former prime minister Malcolm Turnbull.

Mr Turnbull, who was last week ousted in a leadership spill, has flagged his intention to leave Parliament, although he is yet to announce a timeframe.

His resignation could spark a by-election in Wentworth, which takes in Sydney's leafy eastern suburbs.

But with state and federal elections due in the first five months of 2019, the timing of Mr Turnbull's resignation will determine if there is a by-election.

If he is still in the seat at Christmas, it is unlikely voters would be asked to go to the polls three times in close succession.

Ms Forster could be in for a pre-selection battle against former diplomat Dave Sharma and former acting federal director of the Liberal Party Andrew Bragg.

Malcolm Turnbull won the seat of Wentworth in 2004. ( ABC News: Matt Roberts )

Mr Abbott said his sister was a wonderful competitor.

"She and I, famously, have had our differences, but she is an outstanding individual," he said.

ABC election analyst Antony Green said the seat was not particularly conservative.

"Wentworth is a safe Liberal seat, but it's a small L electorate, so as long as they are careful with their candidate selection they will win," he said.

"There will several candidates because it is a prized electorate. It is the sort of seat that potential cabinet ministers hold, but the candidate must also have good local credentials."

More candidates emerge

Another City of Sydney councillor is also considering a tilt at the seat, but as an independent.

Kerryn Phelps says she has been encouraged by messages of support from people wanting her to run in Wentworth.

Dr Phelps works as a GP in Double Bay and is a former president of the Australian Medical Association.

She ran on a ticket with Sydney Lord Mayor Clover Moore as her deputy to win her council spot in 2016, but has since had a falling out with Clover Moore and stepped down as Deputy Mayor.

"I'm watching the situation closely," she told the ABC.

Ms Forster and Dr Phelps are friends, working closely on the Marriage Equality Campaign. Dr Phelps was also a guest at Ms Forster's wedding earlier this year.

The Greens also believe they can be competitive in the seat, and have already announced Waverley Deputy Mayor Dominik Wy Kanak as their candidate.

The Bondi local would be the first Torres Strait Islander to be elected to Federal Parliament, should he pull off a surprise win.