Uniform guidance for family gatherings at Christmas must be devised between all four nations of the UK, political leaders have been urged.
Boris Johnson, Nicola Sturgeon, Mark Drakeford and Arlene Foster were warned that their governments must "accept the inevitability" that people will travel over the festive period.
The call came in a letter from the Liberal Democrats in Scotland, Wales and England - together with the Alliance Party of Northern Ireland.
They said guidance cannot be made in isolation given the "interlinked" nature of life in the UK, and called for a "four nations summit" to agree a plan.
The letter states: "It therefore falls on you and your counterparts to work across governments to explore workable solutions that can enable travel to happen safely.
"To manage the implications for public health, we are urging you to hold a four nations summit to co-operate on students' return, to agree uniform guidance on the number of people who can gather, and to explore how best to expand travel options to allow social distancing."
It is signed by Lib Dem leader Sir Ed Davey, as well as his Scottish counterpart Willie Rennie, Welsh Lib Dem leader Jane Dodds and Alliance Party deputy leader Stephen Farry.
Sir Ed said: "No one country can manage this challenge in isolation. The fractured rules across the UK have already been incredibly difficult to piece together.
"We need a four nations summit to agree on one set of uniform guidance for Christmas that works for families across the UK. Ministers across Britain need to start work on it now."
Despite the UK taking a near uniform approach to lockdown restrictions at the start of the coronavirus crisis in March, the picture across the country is now more fragmented.
In Scotland, First Minister Ms Sturgeon has said her Government is looking at phased term dates and possible testing of students, and issues of people returning home where there are vulnerable people.
Welsh First Minister Mr Drakeford has said the current "firebreak" restrictions should give a pathway to Christmas "without needing a period of this severity of restraint between now and then".
And in England, Downing Street has said it is the Government's "ambition to ensure that people may celebrate Christmas as a family this year".
