Welsh First Minister Mark Drakeford said it was not “proportionate” to include children aged under 12 in the restriction given that they do not spread Covid-19 as much as older children and adults or generally get as ill.
Scotland’s First Minister Nicola Sturgeon has adopted a similar strategy.
Amid signs of a growing Tory revolt on the restriction, former minister Tim Loughton said that applying the Rule of Six to include young children was “not sustainable” and that the “most likely victims will be families who just want to get together to celebrate Christmas or other special family occasions”.
However, Health Secretary Matt Hancock defended the new rule.
A Department of Health and Social Care spokesman said: “We understand that for many this will mean changing long-awaited plans or missing out on precious moments with loved ones, but this sacrifice is vital to control the virus for the long term – and save lives.
“These measures will be kept under review and will not be in for any longer than they have to.”
Tough new Covid-19 restrictions were expected to be ordered today across Birmingham, Britain’s second city of over 1.1 million people. including a ban on households meeting in each other’s homes. It was prompted by a rise in infections.
But the splits on the flagship Rule of Six policy between different nations of the UK deepened the controversy over the toughening of social distancing rules to try to get a grip on the surge in cases.
Boris Johnson and Mr Hancock, despite reported opposition from other Cabinet ministers but backed by Government medical and scientific chiefs, have gone for a very clear-cut and easier to enforce Rule of Six indoors and outdoors, with limited exemptions.
It will come into force on Monday.
But it means that a family with three children could not go for Christmas lunch with two grandparents, if the rule is still in place then, as the group would be seven.
In contrast, the Welsh adminstration has excluded children under 12 from the rule which will also not apply outdoors.
Mr Drakeford told BBC Breakfast: “It is not proportionate to include them in the number of six.
“We are required by our regulations to test everything we do against the test of proportionality We did that yesterday, and we decided it was not proportionate to include young children who are not vulnerable to coronavirus, or to spreading it in the way that adults are, so therefore we are not including them.”
Pressed on why the Rule of Six would not apply outdoors in Wales as in England, he added: “We still have a maximum number of 30 people who can meet outdoors at any one time, but we have no evidence at all in Wales that the virus is being spread by people meeting together in the open air. I think the evidence on this has been very clear for a long time.”
But, adding to the confusion, in Scotland the Rule of Six will apply indoors and outdoors and will be restricted to two households meeting.
Children under 12, though, from within the two households will not be counted in the new limit of six people.
Professor Jason Leitch, Scotland’s National Clinical Director, admitted that the rules were getting “more complicated” given the national differences.
On the Rule of Six, he told BBC Breakfast: “Kids have a very mild course under 12s if they get the disease at all.
“They do transmit the disease, maybe not quite as much as older kids because they don’t get as many symptoms.
“The other balance you are trying to draw here is kids need to play..it’s an essential part of their social upbringing.”
In Westminster, the Government is under growing pressure to amend its current Rule of Six.
Former Tory education minister Tim Loughton told the Standard: “Including young children in the Rule of Six is not sustainable and not proportionate.
“Clearly the most likely victims will be families who just want to get together to celebrate Christmas or other special family occasions.”
Instead, he argued, the restrictions should be targeted at people socialising “irresponsibly and flouting the rules”.
Conservative MP Sir Desmond Swayne told Times Radio that the Rule of Six was “absolutely grotesque”.
Veteran Tory MP Sir Christopher Chope complained that MPs have not been able to debate the introduction of the new social distancing regulations.
He told the Commons: “What we are talking about is the most draconian introduction of new restrictions on our liberty with criminal sanctions and we need to be made aware of what’s happening and given the opportunity of debating it.”
Downing Street was this morning flatly ruling out a change to exclude young children.
A minister denied most Cabinet ministers at a meeting which discussed the Rule of Six wanted it expanded to more people.