It comes as the party recorded a dip in popularity according to a major national poll, with Senator Hanson facing criticism over a recent trip to Europe.
In a video interview published in 2025 and first reported by the Nine newspapers, Senator Roberts questions 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," Senator Roberts 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."
Senator Roberts also questioned the severity of the illness, saying if you don't take into account the most vulnerable such as the elderly and immunocompromised, the severity must be low.
"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.
"We were conned."
Senator Roberts said he wrote to then-prime minister Scott Morrison and former Queensland premier Annastacia Palaszczuk requesting "evidence" but didn't receive a reply.
Senator Hanson has come under pressure to sack her long-term political colleague, who has been accused of embracing conspiracy theories and anti-Semitic tropes.
A Roy Morgan poll published on Tuesday showed One Nation's primary vote had dipped 5.5 per cent to 22.5 per cent, while the coalition registered an increase of three per cent to 23 per cent and Labor was unchanged on 27.5 per cent.
Senator Hanson has come under fire since returning from the UK, where she conducted an interview with anti-immigration activist and convicted criminal Tommy Robinson and told a conservative conference Australia had been "flooded" with migrants.
She also visited Italy with billionaire benefactor Gina Rinehart.
Prime Minister Anthony Albanese accused Senator Hanson of using the trip to engage with fringe people and to talk Australia down.
"I find it astonishing that Pauline Hanson has travelled overseas in order to denigrate and talk down Australia," he said.
Speaking to reporters on the weekend, he said Senator Roberts had "a history of promoting conspiracy theories".
"This is a guy who's been elected and re-elected, and endorsed and re-endorsed, multiple times by Pauline Hanson and One Nation," Mr Albanese said.
"And his views are not worthy of being a senator."
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