Boris Johnson has said there is “unanimous agreement” between the four UK nations over unified rules for Christmas gatherings even as the Welsh and Scottish government announced different guidance for the festive period. Wales issued advice recommending a limit of two rather than three households when families form a Christmas bubble. Scotland advised that a bubble – again, ideally of no more than two households – should not meet up for more than one day and avoid staying overnight together. Johnson was due to hold a Downing Street press conference on Wednesday afternoon, which was expected to include the latest guidance for Christmas plans in England. Following warnings from scientists and MPs over a likely surge in coronavirus infections amid an easing of UK rules at Christmas to allow up to three households to gather indoors, talks were held on Wednesday morning. After the call between devolved leaders from Scotland, Wales and Northern Ireland, and Michael Gove, the Cabinet Office minister, Johnson told the Commons that all parties had agreed to keep the same rules in place. There was, Johnson told Keir Starmer at prime minister’s questions, “unanimous agreement across all the UK government, across all the devolved administrations, including members of all parties, including his own, that we should proceed in principle with the existing regulations, because we don’t want to criminalise people’s long-made plans”. But in a sign that the government instead hopes to warn people against too much mixing, he said the public should “exercise extreme caution” when celebrating Christmas. Under the plan, originally agreed among the four nations in November, up to three households will be allowed to gather for five days from 23 to 27 December, or an extra day on either side to allow for travel to and from Northern Ireland. But in a break from the consensus, as Johnson was speaking in the Commons, the Welsh first minister, Mark Drakeford, announced different Christmas guidance, as well as fresh lockdown measures to be imposed in Wales beginning on Christmas Eve. While the Christmas rules will remain the same, the official advice of the Welsh government is that only two households should come together during the five-day Christmas period. Drakeford said: “Here in Wales over the Christmas period the clear message from the Welsh government is that only two households should meet. That is how serious it is in Wales.” Pressed over whether this was a rule or advice, he said: “The message is the same.” Under the Welsh lockdown all non-essential shops, plus leisure and fitness centres and close-contact services, will shut at the end of trading on 24 December. Hospitality premises, including pubs and restaurants, will close from 6pm on Christmas Day. Separately, the Scottish first minister, Nicola Sturgeon, told her daily briefing that her government would be bringing out its own guidance later on Wednesday, “which we hope will be agreed on a four nations basis”. She said those discussions were ongoing. Sturgeon urged people to limit the number of households gathering: “If you do form a bubble you should not meet up for more than one day and not stay overnight, and keep it as small as possible – three is the maximum but two is better … “Unequivocally, the safest way to spend Christmas this year is within your own household and within your own home.” Asked about the apparent contradiction between the assertion of unanimity and the different messages from Drakeford and Sturgeon, Johnson’s spokesman said: “The prime minister was referring to the fact that all four nations have agreed there will be no changes to the laws around Christmas bubbles.” Any change to local guidance by the devolved leaders was, he added, “a matter for them”. A joint statement from the four UK nations is expected later in the day, as well as updated formal government guidance. There are already slight differences between the nations – for example Scotland has a maximum limit of eight people aged 11 or over – and these are expected to remain. The government and devolved administrations have been under intense pressure from scientists, medical experts and some MPs to reconsider the plan. On Tuesday, the British Medical Journal and Health Service Journal published a rare joint editorial saying the government could no longer claim to be protecting the NHS if it went ahead with rash plans to let households mix indoors, without social distancing, and travel across the country over Christmas. Jeremy Hunt, the former health secretary who chairs the Commons health committee, also urged ministers to consider changing the plans for Christmas, saying it would be “a very, very dangerous and precarious situation” for the NHS to enter January with high levels of bed occupancy from Covid.