As Christmas approaches, questions surrounding whether household mixing will be permitted have come to the fore, but scientists have warned that each day’s freedom might require five days of tougher measures to make up for it.

Nicola Sturgeon has said she hopes that a plan for Christmas can be formed in the next couple of weeks, as the four nations consider ways to allow people to spend time with family over the festive period.

However, a senior health official has said any socialising would likely have to be followed by “very responsible” behaviour and a reduction in contacts again.

Reports suggest households might be allowed to mix indoors for a five-day period from Christmas Eve, but a five-day easing could mean a potential 25-day period of tighter measures into January if the Government follows advice from Sage (Scientific Advisory Group for Emergencies).

Andrew Hayward, professor of infectious disease epidemiology at University College London (UCL) and a member of the Scientific Advisory Group for Emergencies (Sage), said mixing at Christmas poses “substantial risks”, particularly for older people, and there is “far too much emphasis” on having a normal festive period.

Prof Hayward told BBC Radio 4’s Today programme: “Mixing at Christmas does pose substantial risks, particularly in terms of bringing together generations with high incidence of infection with the older generations who currently have much lower levels of infection and are at most risk of dying if they catch Covid.

“My personal view is we’re putting far too much emphasis on having a near-normal Christmas.

“We know respiratory infections peak in January so throwing fuel on the fire over Christmas can only contribute to this.”

Asked if people should worry more about the health and welfare of their parents and grandparents than gathering together for a movie over Christmas, he replied: “Well exactly.

“We’re on the cusp of being able to protect those elderly people who we love through vaccination and it would be tragic to throw that opportunity away and waste the gains we’ve made during lockdown by trying to return to normality over the holidays.”

Prof Hayward said he believed “there is a cost” to gathering families together, adding: “When policies are undulating between stay at home to save lives, eat out to help out, the tier system, second lockdown and proposals for an amnesty on social distancing, it’s a highly inconsistent message.

“Whereas in fact the things that people need to do to stay safe and to keep their loved ones safe are relatively simple.

“Avoid, as far as possible, indoor close contact with people outside of your household, avoid crowded places and protect the most vulnerable by not putting them at unnecessary risk.”

“Approaching 1 is not good enough – that still means the infection is increasing,” he said.

“It needs to be clearly below 1 and it needs to get to low levels, rather than the high levels that we still have.”

Asked whether he would impose further restrictions throughout December such as stricter tiers than before lockdown, he said “it is a very difficult balance”.

He added: “We would need to be very mindful of the fact that this last period of the year is absolutely critical economically for many businesses so I think we do need to find a way of allowing them to function, but in a responsible way.”

Speaking at First Minister's Questions today, Ruth Davidson said: "Sage advice has suggested that for every day we release we will need 5 days of tighter restrictions.

"Does the First Minister recognise that figure of 5 days of tightened restrictions for every day of festive relaxation & is that 5:1 ratio part of the planning?"

She added: "What we need to know, is whether these current restrictions actually are the price for relaxation this Christmas. Or whether that bill will be paid by us all in the new year."

Nicola Sturgeon responded saying that she would not speculate until she had a "deeper understanding" of Sage's "five days for every one" advice.

She stressed that if there are fewer Scots with coronavirus in the lead up to Christmas, there will be less chance of passing it on at Christmas time.

The First Minister added that striking the "right balance" is crucial.