Boris Johnson announced in late November that the coronavirus rules would be relaxed over Christmas to allow more people to spend time with each other over the festive period.
But the government is under pressure to scrap the easing amid fears it will lead to a surge in infections.
What are the current plans?
The government will relax the rules for Christmas to allow up to three households to mix between December 23 and 27.
The prime minister announced on Wednesday this relaxation in the law will go ahead and will apply across the entire UK.
What will change?
Cabinet Office minister Michael Gove hold talks with leaders of devolved administrations on Wednesday morning to try and maintain a UK-wide approach.
A “unanimous” agreement was reached to keep the change in law the same across the UK.
But the advice people are given will be different in England, Scotland, Wales and Northern Ireland.
Johnson told the Commons that while three households can mix in England people should “exercise extreme caution”.
In Scotland, first minister Nicola Sturgeon said her “strong recommendation” was that people “stay within your own household and your own home”.
In Wales, first minister Mark Drakeford said “only two” households should mix over Christmas rather than three.
What’s the problem?
There are deepening concerns that the relaxation will lead to a further spike in infections and deaths in the New Year.
In a rare joint editorial, the British Medical Journal and Health Service Journal said relaxing the rules over Christmas would “cost many lives”.
In Canada, the number of Covid cases surged in the weeks after restrictions were relaxed for Thanksgiving.
Chris Hopson, chief executive of NHS Providers, which represents hospital trusts in England, also pointed to a spike in cases in the United States after Thanksgiving.
“The number of cases has gone up by 25 per cent, the number of hospitalisations has gone up by 20 per cent in a fortnight, and the number of deaths has gone up by 60 per cent in a fortnight,” he told the BBC.
Dr Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases in the US, has said the post-Christmas surge could be even worse than the steep rise that followed Thanksgiving.
The Scientific Pandemic Influenza Group on Modelling (SPI-M-O), which advises he UK government, told ministers in November infections could “easily double during a few days of festive season”.