Plans to ease of coronavirus rules at Christmas should be abandoned in order to bring down Covid-19 numbers ahead of a "likely third wave".
A joint plea by the British Medical Journal (BMJ) and the Health Service Journal (HSJ) said the government should "reverse its rash decision to allow household mixing and instead extend the tiers over the five-day Christmas period in order to bring numbers down".
It said the government's current plan - which will see three households allowed to mix for five days from December 23 to 27 - will "boost the numbers [of coronavirus] further as the NHS also struggles with the additional demands of winter".
It added that the current restrictions are "failing to control the virus" and the government should "review and strengthen the tier structure, which has failed to suppress rates of infection and hospitalisation".
The government is resisting pressure to rethink the planned relaxation of restrictions but is urging Britons to "do the minimum that is necessary" when mixing at Christmas.
Minister Steve Barclay said the government is sticking with the relaxations "because we recognise that for people's wellbeing, loneliness for mental health, for many other reasons it is important to enable those families to come together over the Christmas period".
At the suggestion that more people could die due to the slackening of restrictions, Mr Barclay told ITV News that no minister or scientists "can give a prediction as to whether there will be a spike or not in the future".
The loosening of rules was a plan agreed between all four UK nations, but a newly identified, fast-spreading strain of coronavirus, and a surge in infections in a number of areas is causing many people to worry.
Scotland's First Minister Nicola Sturgeon told ITV News she would prefer households not to mix over the festive period and said she would not rule out abandoning the plan for relaxations.
She said she'll be considering with her chief medical officer whether the Scottish government should impose any "immediate additional precautions" to combat the spread of the new Covid-19 strain.
Sturgeon: If you can avoid it, please do avoid it:
London Mayor Sadiq Khan has called on the government to reconsider the Christmas plan because it will lead to "an increase in the spread of the virus".
"In London we're going to go from a situation where we go from tier 2 to tier 3 to tier zero, basically for five days and back to tier 3.
"If we're not careful we could be sleepwalking into a national lockdown in January."
Susan Michie, a member of the government's Scientific Advisory Group for Emergencies (Sage) urged ministers to "reset" advice over Christmas after warning that the UK faced the prospect of a "really bad" third wave of coronavirus infections.
The professor of health psychology at University College London told the BBC: "I still think it is not too late, because transmission rates are going up, we are facing the potential of a really bad third wave come January and February unless we really take steps now to prevent that.
"I think a bit of a reorientation, a bit of a reset on how people are thinking about Christmas, would be really good.
"I know it would be tough, tough for a lot of people, but it is much better than losing loved ones."
In Wales a fresh lockdown before Christmas is being considered, to reduce the risk of the virus spreading when the rules are relaxed.
As things stand, it is sticking with its plan to relax restrictions, but it is not ruling out a U-turn.
Health Secretary Vaughan Gething said it was not the Welsh Government's "preference" to change the easing of restrictions over Christmas but added: "You can never say never. If the virus continues to grow, then we'll need to make choices to keep people safe.
"So nothing is off the table, but it does rely on the choices that each of us are prepared to make."
England’s Chief Medical Officer Professor Chris Whitty reiterated the need for people to be cautious at Christmas when speaking at Monday evening's coronavirus press conference.
He said people should not meet just because they can.
“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," he said.
“And in particular, incredibly careful if they’re around people who are vulnerable, who are at very high risk of this virus."
At the press conference it was announced that all 32 boroughs of Greater London and the City of London, along with parts of Essex and Hertfordshire, will move into the highest tier of Covid-19 restrictions from 00.01 on Wednesday after "very sharp, exponential rises" of coronavirus in the past week.