Tory MP Jacob Rees-Mogg has refused to wear a face mask in a packed House of Commons for the chancellor’s budget.
On Tuesday, new rules ordered staff to wear face coverings while on the parliamentary estate due to rising COVID-19 cases, although the rule doesn't apply to MPs.
But members of the government frontbench were split over the issue as they gathered to hear the budget on Wednesday.
While the prime minister wore a mask alongside other cabinet members, notable exceptions included Commons leader Rees-Mogg and foreign secretary Liz Truss.
Watch: Jacob Rees Mogg: Tory MPs don’t need masks because of our ‘convivial spirit’
He was responding to SNP MP Pete Wishart, who expressed his frustration with the lack of masks on the Conservative benches.
Rees-Mogg said: "It may be that the honourable gentleman does not like mixing with his own side, he may want to keep himself in his personal bubble... and I sympathise if that is the case, but we on this side have a more convivial and fraternal spirit and are therefore following the advice of Her Majesty's government."
A YouGov poll revealed last week more than three-quarters of Brits think that MPs should wear face masks while they're in the Commons.
The survey showed 50% of people say MPs should definitely wear masks in the Commons, with a further 29% saying they probably should.
Just 12% didn't think they should - 7% saying they probably shouldn't and 5% saying they definitely shouldn't - while 9% said they didn't know.
Compulsory mask-wearing on the parliamentary estate applies to staff, contractors and visitors but the Commons authorities said it could not compel MPs to wear masks as they are not deemed to be parliamentary employees.
However, officials said Commons speaker Sir Lindsay Hoyle would encourage elected representatives to put one on in the chamber unless they speak or are exempt.
There was a clear difference in face coverings across the chamber on Wednesday, with universal mask-wearing on the opposition benches.
In contrast, there were more Conservative MPs without masks in the packed chamber than those with.
Conservative former prime minister Theresa May wore a face covering, as did health secretary Sajid Javid.
MPs were urged to wear masks during Wednesday’s budget speech by a coronavirus expert from the World Health Organization (WHO).
Dr David Nabarro, the WHO’s special envoy for COVID-19, said “everybody” should be wearing masks in close confinement with other people, “including our leaders”.
Last week, Javid suggested Tory MPs should be wearing masks in the Commons as he warned further coronavirus restrictions are more likely if face coverings are avoided.
But on Monday, he said wearing a mask in the crowded chamber is a “personal decision” for ministers and backbenchers.
Watch: Key points from the chancellor's Budget