Ministers are considering allowing people to meet friends and family outdoors, the government has confirmed.
It is one of a series of ideas for easing up the coronavirus lockdown, the prime minister’s official spokesman said.
People could meet with others from outside their household and form small groups with them. Those groups would not meet other groups.
The concept of those “bubbles” had been raised earlier on Tuesday by Scotland’s first minister Nicola Sturgeon.
When asked about the plan on Tuesday, the prime minister’s spokesman said: “Broadly the scientific and medical experts have been clear that there is is less likelihood of transmission of this disease outdoors than indoors.
“That will obviously be something we are considering as part of the review.”
He also confirmed that a “range” of ways of easing the lockdown is being looked at, as well as rules that “need to be toughened”.
“Once we have the scientific evidence and we have completed the review process, we will be able to set out what those are,” he said, with his comments coming ahead of the expected publication of how the country will move forward from lockdown on Sunday.
Earlier on Tuesday, Sturgeon told a press briefing that “small defined groups” of people not living in the same house could begin seeing each other outdoors.
The Scottish government published a paper on Tuesday outlining how the lockdown rules could be eased.
“We are considering if and how we could make changes to allow people to meet with a small number of others (the number is under consideration) outside their own household in a group or ‘bubble’ that acts as a single, self-contained unit, without connections to other households or ‘bubbles’,” the government document states.
“It is possible that this option would be introduced first for outdoor meetings, ahead of any change to permit indoor meetings of the bubble.”
People who are more at risk from the virus would not be able to form one of these bubbles, the papers adds, and if anyone in a bubble developed coronavirus symptoms the rest of the group would have to self-isolate for 14 days.
Sturgeon stressed again on Tuesday that the lockdown must continue as it is for now, and is likely to be extended in its current form on Thursday.
“For the moment we do need to stick with the current lockdown restriction,” she said at the briefing.
The UK government’s published death toll now stands at 28,734, with 190,584 confirmed cases.
Data from the Office for National Statistics for deaths in England and Wales – which cover cases where COVID-19 is mentioned on the death certificate, even if it was suspected – combined with the tolls from Scotland and Northern Ireland provides a figure of more than 30,000.
That figure puts the UK ahead of Italy and makes it the worst hit country in Europe and the second worst in the world, behind only the US, which has suffered more than 60,000 fatalities.
Around the world, there are now 3.5 million cases and more than 247,000 deaths, according to Johns Hopkins University.
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Fears remain that relaxing too many restrictions too quickly will result in a second peak of deaths.
“We will only be able to move onto the second phase of this conflict if our five tests have been met,” he said in a Twitter video.
Those are: ensuring the NHS has critical care capacity; seeing a sustained and consistent fall in daily deaths; the infection rate decreasing to “manageable levels”; having enough personal protective equipment and testing supply, and any changes to restrictions not leading to a second peak that overwhelms hospitals.
Johnson said: “The worst thing we could do now is ease up too soon and allow a second peak of coronavirus.”
On Monday, Sturgeon said that while “real and significant progress” had been made in the fight against the coronavirus, it is still spreading too much to ease up on the lockdown.
She said it would be very likely the lockdown is extended on Thursday.
“In the interests of transparency I can’t say for certain right now whether before May 28, or on May 28, I’ll be able to say we’re easing anything but I’m pretty certain right now, albeit a formal decision hasn’t been taken, that I’m not going to be able to announce any meaningful changes at this point, which will be on Thursday May 7,” she said.
The Scottish government is hoping to run 15,500 tests a day by the end of the month as part of its track and trace system, which is seen as the way lockdown measures can start being lifted.