A scientist whose modelling led to the original lockdown in March has warned that people will die as a result of getting infected with Covid on Christmas Day.
Professor Neil Ferguson told the BBC Radio 4 Today programme: "It risks some transmission and there will be consequences of that. Some people will die because of getting infected on that day."
"But if it is only one or two days the impact is likely to be limited. So that is really a political judgment about the cost versus the benefits."
It comes after Boris Johnson's spokesman said his "ambition" is for families to spend Christmas together this year.
"The PM has been clear previously that he is hopeful that in many ways we could be able to get some aspects of our lives back to normal by Christmas," the Prime Minister's spokesman said.
"As I say, we've been clear about the ambition to ensure that people may celebrate Christmas as a family this year."
Most people should expect Christmas this year to be different from previous ones due to the coronavirus outbreak, a Cabinet minister has said.
Chief Secretary to the Treasury Stephen Barclay, speaking as sweeping new restrictions were imposed on millions more people in different parts of Britain, said he hoped families could be together over the festive season.
Asked how he would describe the chances of people having a “normal Christmas” despite Covid-19 restrictions, Mr Barclay told BBC Radio 4’s Today programme: “I would describe it as a shared endeavour for all of us.
“All of us want to be able to enjoy Christmas with our families. And that’s why there is a common purpose here to get the virus down.”
Referring to Christmas, Mr Barclay said: “I think few people expect it to be exactly as it would normally because we will be living with this virus for some time.
“And the chief medical officer and the chief scientific adviser have been very clear on that.
“But, your point really was about the ability of families to spend Christmas together – that is something we all hope to be in a position to do.”
The idea that “we can carry on as we are” and have a normal Christmas “is wishful thinking in the extreme”, a Government scientific adviser has said.
Professor John Edmunds, a member of the Scientific Advisory Group for Emergencies (Sage), said “radical action” would be needed to stem the rise in coronavirus cases, particularly in regions with high incidence of the virus.
Mr Drakeford warned hundreds more people would die from coronavirus across Wales “unless we act now to bring this deadly disease under control”.
He told the Welsh Government’s Covid-19 press briefing: “That’s the seriousness of the position we are in. Our ambition is we will not need to have this level of restriction again in Wales before Christmas.
“I want shops to be able to trade. I want people to be able to prepare. I want to offer people some hope that, provided we all do the right things, then we will still be able to enjoy a version of the holiday that we would have otherwise enjoyed.”
When asked if he envisaged people from outside Wales being prevented from entering the country for Christmas, Mr Drakeford said it was “impossible to predict” how Wales’s attempts to lower the prevalence of the virus “will mesh in with the difficulties faced elsewhere in the United Kingdom”.