Conservative MPs don't need to wear masks during debates because they know each other, Jacob Rees-Mogg has said.
The Commons leader said the party's "convivial, fraternal spirit" meant they were acting in line with government Covid guidance.
This guidance says people in England should cover their faces around "people you don't normally meet".
Tory MPs have largely ditched masks in recent months, but are being urged by opposition parties to wear them.
On Thursday, Labour's shadow Commons leader Thangam Debbonaire said MPs should wear face coverings to set the "best example to the public".
But Mr Rees-Mogg responded that many Labour MPs had been pictured maskless at the the party's recent annual conference in Brighton.
And he claimed they were more likely to cover up "when there are television cameras around".
The SNP's Pete Wishart told Mr Rees-Mogg all MPs should set an example by wearing masks - and that the difference between the Tory and opposition MPs on the issue had become "comic".
Mr Rees-Mogg joked that the SNP MP might not like "mixing with his own side" but the Conservatives "have a more convivial, fraternal spirit and therefore are following the guidance of Her Majesty's government".
Speaking on the BBC's Question Time programme, Conservative vice chairman Andrew Bowie acknowledged that his fellow Tory MPs had been criticised for not wearing masks in Parliament but said the situation with Covid had looked "very different" in the first weeks of autumn.
He said MPs had "a responsibility to set the tone and set an example" and that he was "encouraged" to see more of his colleagues wearing masks in the House of Commons.
Professor Robert West, a health psychologist advising the government as part of the Scientific Pandemic Insights Group on Behaviours (Spi-B), argued that MPs would set an example if they wore masks.
"Actually people who are ambivalent, it gives them a kind of excuse if you like, to say, 'If they're not doing it why should I do it?'" he told BBC Radio 4's World at One.
"It's about leadership. And politicians often talk to members of the public and sports personalities and so on about setting a right example for the public and I do think it behoves them to do the same thing."
Most MPs from opposition parties have been wearing masks in the Commons chamber since full in-person sittings resumed over the summer.
The government is still encouraging people in England to wear face coverings in "crowded and enclosed spaces", although it is no longer mandatory.
On Wednesday, Health Secretary Sajid Javid said mask-wearing was one of several measures that could help lower Covid transmission over the winter.
Speaking at a Covid press conference in Downing Street, he warned restrictions were "more likely" to return if people "don't wear masks when they really should".
He said this included "really crowded" places "with lots of people that they don't normally hang out with".
His statement came just hours after MPs packed into the Commons chamber for Prime Minister's Questions.
Nearly all Conservative MPs, including government ministers, did not wear a face covering during the session.
Liberal Democrat MP Layla Moran said: "It is utter hypocrisy that the public are rightfully being advised to wear masks while Conservative MPs refuse to do so.
"Conservative MPs and ministers have a duty to lead by example and take precautions to protect themselves, their colleagues and staff."
Unions representing parliamentary staff say their members have been told to wear masks in the chamber, and have called for Tory MPs to do the same.
The Prospect union has previously accused maskless MPs of "recklessly undermining" public health messaging, and urged mask-wearing to be more rigorously enforced.
GMB and Unite have called on Commons Speaker Sir Lindsay Hoyle, who enforces the parliamentary dress code, to refuse entry to maskless MPs.
Sir Lindsay has encouraged MPs to continue to wear masks during debates, but has said there is "no meaningful way" for him to enforce this as he does not have the right to stop elected MPs entering the Commons.