Cabinet Office minister Michael Gove discussed the scheduled relaxation with the first ministers of Scotland, Wales and Northern Ireland on Tuesday but they did not confirm a new position.
However, a source in the UK Government said there were no plans to change number of days or households allowed to mix in England, with leaders trying to agree on new safety warnings for Christmas.
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-nation approach.
But her Welsh counterpart Mark Drakeford said the current plans were a “hard-won agreement” and he would “not lightly put it aside” ahead of the first meeting.
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The talks took place after two leading medical journals warned that a lessening of restrictions would “cost many lives” and the British Medical Association (BMA) echoed Labour leader Sir Keir Starmer in demanding an urgent re-think.
Downing Street conceded that the planned five-day Christmas easing to allow three households to mix indoors between December 23 and 27 was being kept “under constant review”.
A UK Government source said Mr Gove and the devolved leaders had a “constructive call”, and added: “There are no plans to change the regulations in England.
“We’re keen to maintain a UK-wide approach and will have further discussions with DAs (devolved administrations) tomorrow morning.”
It was understood talks largely centred on guidance for people to consider whether they should meet elderly or clinically-vulnerable loved ones and to stress that the rules are a limit and not a target.
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.”
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. Another 18,450 infections were also confirmed in labs as of 9am on Tuesday.
Ms Sturgeon earlier told the Scottish Parliament: “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.
“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 “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.
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 the Government “is about to blunder into another major error that will cost many lives”.
“The Government was too slow to introduce restrictions in the spring and again in the autumn,” the joint editorial said.
“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.”
The BMA backed the warning, saying the combination of a third wave in the new year and the typical winter pressures are a “recipe for catastrophe”.
Council chairman Chaand Nagpaul said: “As well as reviewing the rules for Christmas, the Government must also look at what happens when the tinsel is tidied away.
“Now is the time to for everyone to continue to follow the rules and guidance until the vaccine can be rolled out to protect many more of us and allow us to mix freely once more.”
The Prime Minister’s official spokesman said ministers “keep all advice under constant review” in response to suggestions that Christmas arrangements could be restricted to three days or two households.
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 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 enter the strictest Tier 3 restrictions on Wednesday.