Calls for a formal investigation into a "homophobic" smear campaign against Wentworth independent candidate Kerryn Phelps have been backed by her Liberal rival Dave Sharma.
Meanwhile, former prime minister John Howard has urged "grumpy" Liberal loyalists not to jeopardise the stability of the Morrison government with a protest vote in Saturday's by-election.
It was revealed on Wednesday that an anonymous email was being circulated urging voters to back the Liberal candidate over Dr Phelps.
"Please DO NOT vote for her, just choose Sharma as your top choice only," the email states.
"Kerryn was diagnosed with HIV yesterday so no chance she will be running for election."
The former Australian Medical Association boss on Thursday stated: "The whole email is definitely not true."
"Just when you think we've come so far in destigmatising HIV for somebody to use this as a slur in an email in a political campaign shows we've still got a long way to go," Dr Phelps told ABC TV.
"There's no question there's a homophobic element to it, but I think we need to rise above all of that and focus on the issues that are really important to this by-election and the future of Australia."
Dr Phelps says there's no evidence the Liberal Party was behind the email and Mr Sharma insists the attack is "despicable".
"All I can say is I repudiate this email entirely and thoroughly," he told reporters while touring the electorate with Mr Howard on Thursday.
He backed any investigation by police or the electoral commission arguing the attack "should be confronted and combated".
Mr Howard spoke to angry voters threatening to punish the government for ousting their former member - then-prime minister Malcolm Turnbull.
"I want to say to any normal Liberal voters in Wentworth who may be a bit grumpy at the present time, who may feel a bit disillusioned, you cannot risk a protest vote," he said in Double Bay.
"If enough people decide to register a protest vote, the seat could go to an independent and that would rob the Morrison government of its working majority."
One voter on the end of a Howard handshake was performer Leo Sayer who later told reporters he'd be voting Labor because the government "is going the wrong direction".
Dr Phelps has capitalised on the discontent reminding voters they were heading to the polls on Saturday "because a prime minister in the middle of his term was removed from office for no rational reason".
ABC election analyst Antony Green says if Dr Phelps finishes second on first preference votes behind Mr Sharma he expects 80 to 85 per cent of Labor and Greens preferences will flow her way.
To withstand that the Liberal Party candidate's primary vote "has to be in the high-40s", he told ABC radio on Thursday.
Leaked Liberal polling suggests Mr Sharma's primary vote could be as low as the mid-30s. The polling, published in The Australian this week, suggested Dr Phelps could win 55 to 45 per cent on a two-party preferred basis.
Mr Howard said there was no "unlosable seat" in modern politics - even blue-ribbon Wentworth which has belonged to the Liberal Party and its predecessors since federation.
Australian Associated Press
