The Prime Minister has conceded Liberal candidate Dave Sharma is likely to lose Saturday's Wentworth by-election and therefore his Government's majority in Canberra.

Key points: The Liberals hold Wentworth on a 17.7 per cent margin

The Liberals hold Wentworth on a 17.7 per cent margin The party, or its predecessors, have held the electorate since Federation

The party, or its predecessors, have held the electorate since Federation Hecklers interrupted the Prime Minister's press conference in Bronte this morning

Speaking on the eve of the vote, Scott Morrison was repeatedly pressed about Mr Sharma's chances against high-profile independent Kerryn Phelps.

As Prince Harry and Meghan made a jubilant arrival on the sands at Bondi, two beaches away the mood was more awkward at Bronte, where Mr Morrison's press conference was interupted by hecklers.

The Coalition hold a one-seat majority in the House of Representatives and while losing Saturday's by-election would not bring down the Government, it would make passing legislation much more difficult.

The Liberal Party and its predecessors have held Wentworth since Federation and their current buffer is 17.7 per cent.

Mr Morrison said the seat was likely to change hands this weekend.

Q: Is he the underdog in this race?

Morrison: I've always said that.

Q: Do you expect that on balance he will lose?

Morrison: I've been saying that for the last couple of weeks.

Q: Do you expect that on balance he will lose?

Morrison: I think the expectations are clearly set in this direction.

The by-election was sparked after former prime minister Malcolm Turnbull resigned from Parliament, following an August leadership spill.

While he has remained abroad for the duration of the campaign, yesterday the Liberals wheeled out another former PM, John Howard, to campaign with Mr Sharma.

"As John Howard said yesterday, the events of a couple of months ago would have caused a great deal of anger and outrage here in Wentworth," Mr Morrison said.

"I know, I was in the Parliament."

That statement sparked an awkward exchange with a heckler, who told the Prime Minister that voters were "still" angry.

A dozen members of the public gathered to hear the press conference on Friday morning, with a number of people interrupting the Prime Minister yelling: "What about climate change?"

Liberal candidate Dave Sharma and Scott Morrison on the campaign trail. ( AAP: Mick Tsikas )

Despite initially guaranteeing confidence and supply to the Morrison Government if elected, Dr Phelps' rhetoric this week has been more vague on that subject.

When she launched her campaign, the former Australian Medical Association president instructed voters to "put the Liberals last", but has since preferenced them above Labor on her how-to-vote cards.

"In the last 24 hours we've heard that the leading independent candidate has said that she could not guarantee not bringing down the Government on a vote of confidence in the Government," Mr Morrison said.

"Now that's serious stuff."