Boris Johnson has urged people to keep Christmas celebrations "short" and "small" to reduce the risk of spreading Covid over the festive period, reports BBC.
Restrictions will still be relaxed between 23 and 27 December - but the PM said people should "think hard" before meeting friends and family.
Three households will be allowed to meet - apart from in Wales where a law change will allow just two households.
And in Scotland people are being asked to only meet on one of the five days.
It comes as the UK recorded a further 25,161 coronavirus cases on Wednesday, along with 612 deaths within 28 days of a positive test.
Mr Johnson said the law was remaining the same in England but "a smaller Christmas is going to be a safer Christmas and a shorter Christmas is a safer Christmas".
Speaking at a Downing Street press conference, he said the rules allowing three households to meet over five days were "maximums, not targets to aim for". "It's always going to be safest to minimise the number of people you meet," he said.
After the news conference, the UK, Scottish and Welsh governments issued a joint statement saying this "cannot be a normal Christmas" and that they "strongly" recommended people stayed at home.
They advised people who were visiting others to stop unnecessary social contact as soon as possible and for at least five days before travelling. No one should visit another household if they were ill or self-isolating, they said.
Mr Johnson also advised people to avoid travelling from "high prevalence" areas to those with lower rates of coronavirus and not to stay away from home overnight if possible.
Mr Johnson urged caution over seeing elderly or vulnerable relatives, saying that since the vaccine was being rolled out to these groups "by the early months of the new year", they would be able to meet people more safely soon.
"Whatever your plans for Christmas, please think carefully about avoiding crowds in the Boxing Day sales, and no one should be gathering in large groups to see in the new year," he added. England's chief medical officer Prof Chris Whitty warned: "Just because you can do something doesn't mean it's sensible in any way."
"Any kind of period where people come together in groups that otherwise wouldn't meet leads to an increase in risks and that will lead to an increase in hospitalisations and deaths," he said.
He urged people to keep their Christmas celebrations small, short and local to reduce these risks.
But in Wales new guidance on households mixing will be put into law, meaning only two households - plus an additional single person who lives alone - will be able to form a Christmas bubble.
UK leaders had come under pressure to review the guidance for Christmas amid rising infections.
In November, all four nations agreed that three households would be able to form a Christmas bubble between 23 and 27 December, allowing them to mix indoors and stay overnight.
However, the Welsh government has now decided Christmas bubbles should be limited to two households - plus an additional single person who lives alone.
First Minister Mark Drakeford also announced the country would head back into a stay-at-home lockdown as soon as the Christmas period was over.
