The prime minister is expected to set out the basis of his festive period plans in the Commons later on Monday, as he reveals his toughened system of tiered controls for England when lockdown ends on 2 December.
The government is thought to be planning a seasonal break from the rules of less than one week – with recent reports suggesting that up to four households could be allowed to form a temporary bubble.
It would mean one family could decide to spend the key dates with both sets of grandparents, or a single person meeting up with two groups of friends who live together.
Officials from the four nations of the UK have been discussing a shared plan to allow family gatherings and travel across the country over the Christmas period.
The Cabinet Office said on Sunday that leaders from England, Scotland, Wales and Northern Ireland had all endorsed an objective of “some limited, additional household bubbling” over the holiday.
However, the Scottish government said “no agreement has been reached”. So any firm details on the Christmas arrangements will have to wait until at least Tuesday to allow Nicola Sturgeon’s cabinet time to sign off on the plans.
While Mr Johnson is hoping that Christmas gatherings will help head off any opposition to his post-lockdown plans, many public health experts have warned it will give Covid-19 another opportunity to spread.
Professor Linda Bauld, professor of public health at the University of Edinburgh, said people should decide for themselves whether it is safe to meet relatives for the holiday – even if governments allow it.
“It is up to us to decide, even if government says ‘Okay, you can get together indoors with other people’,” she told BBC’s Good Morning Scotland.
“Let’s all make our own risk assessment about the people we care about and ourselves and say how are we going to apply that to our own personal circumstances.”
Health secretary Matt Hancock claimed on Monday that if the festive easing of rules was “cautious and careful” then the government would be able to “mitigate” against a rise in Covid transmissions.
Calum Semple, professor of child health and outbreak medicine at Liverpool University, suggested it would be better to sanction some limited get-togethers, otherwise there would be more extensive rule-breaking. “In reality we can’t ban Christmas, and to do so would simply lead to breaches.”
Dr Michael Tildesley, associate professor in infectious disease modelling at Warwick University, said it was vital extended bubbles were maintained exclusively.
The Sage member said: “What you don’t need to do is go and see your grandparents and then go out to see your friends in the pub on the same day, and go back to your grandparents, because that’s where the real risk is.”