The would-be Tory MP for Wakefield has urged people to vote Conservative because "we still trust GPs" after Harold Shipman killed 250 people.
Nadeem Ahmed is bidding to replace Imran Ahmad Khan, the former Conservative MP who triggered a by-election in West Yorkshire after he was jailed for sexually assaulting a 15-year-old boy.
The Tory candidate left people shocked, however, after he said the ex-MP was "one bad apple" before launching into a bizarre speech about Shipman.
"It was the right thing to happen to him," Mr Ahmed told the Telegraph.
"He's in prison, which is the right place. As a teacher, a father, and as a human being, what he did was wrong.
"He's been convicted of that offence, and I cannot stand here and say that was right. It was absolutely disgusting. And the people of Wakefield know that he was one bad apple."
He added: "Harold Shipman committed suicide in Wakefield prison. He was a GP, he was a trusted professional, just like teachers and others.
"When they put a vaccine in our arms, we trust what they are putting in us.
"Have we stopped trusting GPs? No, we still trust GPs and we know that he was one bad apple in there."
Mr Ahmed also repeated the comparison in an interview with ITV, saying: "The people of Wakefield understand there's bad apples... look at Harold Shipman. He committed suicide in Wakefield prison, but do we trust our doctors?"
Shipman was convicted of the murder of 15 of his patients, but a subsequent inquiry estimated that the true figure was closer to 250.
In most cases, he injected elderly patients with a lethal dose of diamorphine before signing a death certificate claiming they had died of natural causes.
Labour is predicted to win the by-election as embattled Mr Johnson faces the fallout from Partygate and continued questions over whether he breached his own ministerial code.
The Conservatives also face losing a second by-election, most likely to the Liberal Democrats, in Tiverton and Honiton. The former Tory MP Neil Parish resigned last month after admitting looking at porn on his phone in the Commons.