Veteran MP and former House of Representatives speaker Bronwyn Bishop is making her final pitch to Liberal party members in the hope of keeping her job.

Key points: Ms Bishop faces challenge from Walter Villatora and Jason Falinski

Ms Bishop faces challenge from Walter Villatora and Jason Falinski Tony Abbott and NSW Premier wrote references for Mr Villatora

Tony Abbott and NSW Premier wrote references for Mr Villatora 'Choppergate' scandal a potential problem with voters for Ms Bishop

Ms Bishop is facing a Liberal preselection vote in the Sydney suburb of Dee Why, as she fights to retain her seat in the blue ribbon electorate she has held for 22 years.

Ninety-six preselectors are set to determine her fate.

Asked if she felt confident about receiving the nod from her Liberal colleagues, Ms Bishop declined to say.

Some party elders publicly criticised Ms Bishop's decision to recontest the northern Sydney seat of Mackellar, arguing that it is time for the 73-year-old to retire and allow new blood into the ranks.

Moderate state government staffer Jason Falinski and hard-right candidate Walter Villatora are widely seen as the biggest threats to Ms Bishop.

Mr Villatora was this week publicly endorsed by former prime minister Tony Abbott, who once described himself as the "political lovechild" of Ms Bishop and John Howard.

"I'm not going to make any adverse comments on my colleague of very long standing," Mr Abbott told 7:30 on Thursday.

"Obviously I do know some of the candidates in the Mackellar pre-selection.

"One I've worked with very, very closely and I respect very much, and that's why I've given him a reference.

"But in the end it's up to the pre-selectors of Mackellar to make what they think is the best choice."

'Choppergate' sparked Bishop's decline

Ms Bishop resigned as speaker of the House after she billed taxpayers $5,000 for a short helicopter charter flight between Melbourne and Geelong, prompting a review of politicians' entitlements.

Tony Abbott says he is backing Walter Villatora over Bronwyn Bishop for pre-selection in Mackellar. ( AAP: Alan Porritt )

At the time, Mr Abbott stood by Ms Bishop, but joined NSW Premier Mike Baird in writing a refererence for Mr Villatora in February.

Professor David Flint, who is a friend of Ms Bishop, told AM she had done a good job in parliament, but it might be time to move on.

"She was certainly a very vigorous and strong member of Parliament," he said.

"There is a time, of course, when we all have to move on from our positions.

"She will be regarded very highly within the community, notwithstanding a minor peccadillo."