Top Tory Jacob Rees-Mogg has said opposition MPs could avoid wearing face coverings in the House of Commons chamber, just like the majority of Conservatives, by simply working "a bit harder" to meet each other more.
The leader of the House followed Health Secretary Sajid Javid by suggesting colleagues who meet each other regularly do not need to wear face coverings.
Scottish Nationalist Party (SNP) MP Pete Wishart was up in arms about Tory MPs appearing in a packed Commons chamber during Prime Minister's Question without wearing masks - just one day after the government said people should consider wearing them in crowded places when surrounded by people they don't regularly meet.
He told MPs: "This is now getting beyond a joke. The scenes from a packed PMQs yesterday were simply a disgrace with barely a facemask on a Tory mush (face).
"The House staff are now getting increasingly nervous and anxious about what they are observing. It seems like the Tories have absolutely no regard whatsoever about the safety of their colleagues and the staff who are here to support and help us.
"The government's own advice states: 'wear a face covering in crowded and enclosed settings where you come into contact with people you don't normally meet'.
He added: "The Health Secretary excused the Tory no-face masks policy, suggesting you can't catch Covid from friends. Isn't it the case that this House is sending the worst possible message to the country and contributing to all sorts of confusion?"
Mr Rees-Mogg hit back, accusing opposition MPs of not attending Parliament regularly enough to avoid the need for masks.
"The advice from Her Majesty's Government on face coverings is that they are not required by law in the workplace, and the government removed the legal requirement to wear face coverings in public places in indoor spaces.
"If you are in a crowded indoor space where you come into contact with people you don't normally meet, wearing a face covering can help reduce the spread of Covid.
"Is it not interesting that he, and perhaps this applies to the nationalists generally, do not normally meet other MPs? Perhaps, this is because they are not very assiduous in their attendance in the House of Commons?"
Mr Rees-Mogg added: "And is it not a pity that some people don't like to come to Parliament? And if they came a bit more, they worked a bit harder, if they put their elbows to the grindstone, wherever you put your elbows, elbows to the wheel, they might not need to wear face coverings either because they would meet members of Parliament more regularly."
The government set out how it will fight Covid through winter on Tuesday, with the plan focusing on vaccines, with new advice on face coverings and indoor gatherings.
Ministers were criticised that same day for not wearing face masks during a Cabinet meeting.
Health Secretary Javid justified the lack of masks suggesting they were not needed because those at the meeting were not strangers.
"At the right time, people should wear masks and we set out guidelines around that. A lot of people do, particularly if you're in a crowded place with lots of strangers," he told ITV News.