Urgent talks between UK leaders on the easing of coronavirus restrictions over Christmas will resume on Wednesday amid increasing pressure to halt the plans over concerns of a fresh spike in Covid-19 cases.
Cabinet Office Minister Michael Gove discussed the scheduled relaxation with the leaders of Scotland, Wales and Northern Ireland on Tuesday but they did not confirm a new position on whether to change the plan or strengthen their safety warnings.
Scotland's First Minister Nicola Sturgeon earlier argued there is a case for reducing the planned freedoms to combat a rise in infections and indicated she could break with the four-nations approach.
But her Welsh counterpart Mark Drakeford said the current plans were a "hard-won agreement" and that he will "not lightly put it aside" ahead of the first meeting.
The talks took place after two leading medical journals warned that a lessening of restrictions would "cost many lives" and Labour leader Sir Keir Starmer demanded an urgent review.
Downing Street conceded that the planned five-day Christmas easing to allow three households to mix indoors between December 23-27 was being kept "under constant review".
After the meeting, a Scottish Government spokeswoman said: "The four nations call was a good opportunity to review the position on Christmas and discuss whether the messaging or guidance requires to be reinforced."
The talks will reconvene on Wednesday, both the Welsh and Scottish governments said.
A spokeswoman for Northern Ireland's First Minister Arlene Foster and Deputy First Minister Michelle O'Neill said they would discuss the situation with medical and scientific advisers before bringing an update to the Executive on Thursday.
The meeting was held as the Government said a further 506 people had died within 28 days of testing positive for Covid-19, bringing the UK total to 64,908. A further 18,450 coronavirus infections were also confirmed in labs as of 9am on Tuesday.
Ms Sturgeon earlier raised the prospect of splitting with the other nations' approach and argued that it may be necessary to reduce the number of households allowed to mix, and the period they are allowed to meet for.
"I do think there is a case for us looking at whether we tighten the flexibilities that were given any further, both in terms of duration and numbers of people meeting," she told the Scottish Parliament.
"And I will consider the views of the other nations – if we can come to a four-nations agreement, I think that would be preferable.
"If that is not possible, then of course we will consider within the Scottish Government what we think is appropriate."
In Wales, Mr Drakeford told the Senedd that "the choice is a grim one, isn't it?" and highlighted "heart-rending pleas" he has received from people to not reverse the existing plan.
"I think the choice is an incredibly difficult one," he added.
Sir Keir urged Boris Johnson to call an emergency meeting of the Government's top level Cobra committee within 24 hours to assess the situation.
In a letter to the Prime Minister, the Labour leader accused ministers of having "lost control of infections" and warned that "the situation has clearly taken a turn for the worse since the decision about Christmas was taken".
"If you conclude with Government scientists that we need to take tougher action to keep people safe over Christmas, then you will have my support," Sir Keir said.
Earlier, the British Medical Journal and Health Service Journal published a rare joint editorial calling for the "rash" decision to relax social distancing measures over the festive period to be scrapped.
They said that the Government "is about to blunder into another major error that will cost many lives".
In response to suggestions that the Christmas arrangements could be restricted to three days or two households, the Prime Minister's official spokesman said: "We have set out the guidance for the Christmas bubbling arrangements.
"But... we obviously keep all advice under constant review."
"We believe the government is about to blunder into another major error that will cost many lives. If our political leaders fail to take swift and decisive action, they can no longer claim to be protecting the NHS" @fgodlee@HSJEditorhttps://t.co/cbgphEQVjr
— The BMJ (@bmj_latest) December 15, 2020
The joint editorial warning noted that when the Government devised the Christmas plan "the Covid-19 demand on the NHS would be decreasing".
"But it is not, it is rising, and the emergence of a new strain of the virus has introduced further potential jeopardy," they added.
"Members of the public can and should mitigate the impact of the third wave by being as careful as possible over the next few months. But many will see the lifting of restrictions over Christmas as permission to drop their guard.
"The Government was too slow to introduce restrictions in the spring and again in the autumn.
"It should now 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 in the advance of a likely third wave."
Reducing the planned easing may further anger Tory backbenchers who oppose restrictions, but a poll suggested the majority of Britons believe the relaxation should be scrapped.
The YouGov survey of 3,856 adults on Tuesday indicated that 57% believe the plans should be dropped and that the current rules should remain in place during the festive period.
Some 31% said the easing should go ahead as planned, while 12% said they were unsure.
The relaxation of regulations looms as London, much of Essex and part of Hertfordshire will enter the strictest Tier 3 restrictions on Wednesday.