In a video interview published in 2025, Senator Roberts questioned the extent of deaths during the early days of the pandemic.
"Major news broadcasters had these videos of people dying in their droves in makeshift morgues in the streets of New York, the streets of Beijing, the streets of Italy," he told a forum hosted by podcaster Sam Hope.
"We thought it is pretty serious from what we've seen. We didn't realise until fairly recently that those were all staged. They're bullshit."
One Nation MP Barnaby Joyce on Wednesday distanced himself from the comments, while adding he didn't want to throw his colleague "under a bus".
"Malcolm's a great guy, he's so smart, but on that issue I don't concur with his view," he told Sky News.
"He's entitled to have it and I'm entitled to have mine."
Mr Joyce also apologised for his bizarre outburst during an interview with ABC's 7.30 on Monday night, during which he yelled at his dog to sit down midway through a sentence.
"You couldn't hear it, but I could. And it was under my skin," he said.Â
"It was under the floor, under the deck and it was just barking incessantly."
In the interview, Senator Roberts also questioned the severity of COVID, saying people were "conned" about its impact.
"The chief medical officer who was involved in staging a lot of the lies we were told by the bureaucracy ... the chief medical officer's graphs showed low to moderate severity," he said.
The senator added he wrote to then-prime minister Scott Morrison and then-Queensland premier Annastacia Palaszczuk requesting "evidence" but didn't receive a reply.
The One Nation senator has previously been accused of promoting conspiracy theories and anti-Semitic tropes.
He has not directly addressed the criticisms in recent days, although he took to social media to accuse mainstream media outlets of "selective cherry picking and dishonest distortions ... on behalf of their uniparty mates".
One Nation has faced increasing scrutiny as it rises in the polls, soaring above both the coalition and Labor in some surveys.
However, a Roy Morgan poll published on Tuesday showed the anti-immigration party's primary vote dipped more than five percentage points to 22.5 per cent in the space of a week.
The poll, conducted during One Nation leader Pauline Hanson's widely publicised trip to Europe, showed coalition support rising to 23 per cent and Labor unchanged on 27.5 per cent.
Senator Hanson has come under fire since returning from the trip, during which she was seen holidaying with billionaire donor Gina Rinehart.
She also met with anti-immigration activist and convicted criminal Tommy Robinson and told a conservative conference Australia had been "flooded" with migrants.
Prime Minister Anthony Albanese accused the One Nation leader of using the trip to engage with fringe people and to talk Australia down.
Speaking to reporters at the weekend, he said Senator Roberts had "a history of promoting conspiracy theories".
"His views are not worthy of being a senator," Mr Albanese said.
