A normal Christmas for people across the UK is “extreme wishful thinking” unless urgent measures are introduced to beat back coronavirus, one of the government’s top scientific advisors has said.
Professor John Edmunds, a member of the Scientific Advisory Group for Emergencies (Sage), said "radical action" would be needed to halt the rise in Covid-19 cases sweeping the UK.
It comes as ministers indicate that they think it could be possible for families to spend Christmas together, despite the accelerating spread of the virus.
Speaking on Friday Steve Barclay said the government hoped to be in a position where household contact was possible, though he warned the situation might not be "be exactly as it would normally".
But critics, including former chancellor George Osborne, accused the government of "optimism bias", while Labour called for a national "circuit breaker" lockdown now to clear the way for the festive season.
"The only way that we can have a relatively safe and normal Christmas is if we take radical action now to reduce incidence - at the very least in high incidence areas - and keep the incidence low across the country by implementing a package of measures to reduce social contacts," Professor Edmunds told the PA news agency.
"The notion that we can carry on as we are and have a Christmas that we can celebrate normally with friends and family is wishful thinking in the extreme."
Labour shadow chancellor Anneliese Dodds told the BBC that not locking down immediately would have "enormous economic cost" by dragging a second wave of the virus into the Christmas period, with people "changing their consumption behaviour".
"The tier system so far has not worked to reduce infections," she said.
"What we are looking at unfortunately - given the Government doesn't seem to be willing to shift on this when half-term holidays are coming up ... is an increasingly difficult situation in lots of parts of the country."
Ms Dodds said the current response was creating a crisis that was "drawn out and spread across the country" resulting in "many fewer people going out to buy things".
Questioned about the country's prospects for Christmas, chief secretary to the Treasury Steve 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 chief scientific advisor have been very clear on that.
"Your point was really about the ability of families to spend Christmas together: that is something we all hope to be in a position to do."
He added: "I would describe it as a shared endeavour for all of us. You and I, everyone listening to the programme wants to be able to enjoy Christmas with our families, that's why there's a common purpose here, to get the virus down."
Household mixing is largely banned under tier 3 rules imposed across large swathes of the country, and this situation would need to be reversed for family gatherings to take place.
Mr Barclay said the government's current strategy "strikes the balance in getting the virus numbers down but doing so in a way that process as many jobs as possible".
But former chancellor George Osborne sounded a note of caution about "optimism bias", warning: "I think this constantly telling us the crisis is going to be over soon hasn't really worked for the government and they're having to get back into the much tougher political message, which is a long-hard slog".
Stricter rules were imposed on nearly six million people on Friday, as Greater Manchester joined Liverpool and Lancashire in tier 3. South Yorkshire is also set to move into the highest tier on Saturday.
Residents of Wales are also being asked to stay at home for a national 17-day “firebreak” lockdown.
Under the highest level of rules imposed in England, pubs and bars are closed unless they offer “substantial” meals, and households are banned from mixing.