Hopes of normal family gatherings at Christmas have been thrown into doubt amid rising Covid infections partly due to a newly-identified variant of the virus.
Scientists have warned that the planned easing of restrictions over the festive period would cause a spike in infections, as London and some surrounding areas prepare to enter Tier 3.
The capital and parts of the commuter belt will be placed under the toughest measures – forcing the closure of hospitality – from Wednesday following a “very sharp” rise in cases.
Health Secretary Matt Hancock said higher infections in the South East may be in part due to a newly identified variant of coronavirus which is growing faster than the existing one.
The discovery sparked fresh concerns over plans to allow up to three households to mix indoors from December 23 to 27 – with fears the country will “pay the price” in the new year.
David Nabarro, a World Health Organisation (WHO) special envoy working on Covid-19, said the price of such a relaxation “could well be very high”.
Urging people to think carefully about their plans, he told Times Radio: “Just ask yourself, is there any way in which you can perhaps not have the family get-togethers this year?
“It’s much better not to do it when there’s this kind of virus about.”
Professor Stephen Reicher, of the University of St Andrews, said: “Right now we are heading towards disaster.
“Given high levels of infection across the country and the increasing levels in some areas (such as London) it is inevitable that if we all do choose to meet up over Christmas then we will pay the price in the new year.”
The chief executive of the NHS Confederation, Danny Mortimer, questioned whether “these rules will be enough to protect the population in the short term”.
Tory former minister Stephen Hammond, who represents Wimbledon, told BBC Two’s Newsnight that he thought there would be a “rethinking” over whether it is appropriate for families to gather at Christmas.
Mr Hancock said people should be “extremely careful” about who they mix with in the run-up to Christmas if they are planning to see elderly relatives over the festive period.
England’s chief medical officer Chris Whitty also struck a cautious tone, saying people should not meet at Christmas just because they can.
He said: “The point of this (relaxation of rules) is for, under certain circumstances, families who wish to, to get together, but they really have to be very, very careful.
“And in particular, incredibly careful if they’re around people who are vulnerable, who are at very high risk of this virus.”
Downing Street insisted there were no plans to change the “Christmas bubble” policy despite the fears.
The decision to move London and parts of Essex and Hertfordshire into Tier 3 affects almost 10.8 million people and means 61 per cent of England’s population will be under the toughest restrictions from Wednesday.
It will have a devastating impact on the capital’s nightlife, with theatres forced to shut and pubs and restaurants closed apart from takeaway and delivery services.