The Prime Minister said he wanted to be “stricter” on insisting people wear mouth and nose coverings in confined spaces where they are meeting people they do not normally see.
Mr Johnson was pictured wearing a face covering for the first time during the pandemic while visiting businesses in his Uxbridge constituency on Friday.
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And in an online question and answer session with the public, he said: “I do think we need to be stricter in insisting people wear face coverings in confined spaces where they are meeting people they don’t normally meet.
“We are looking at ways of making sure that people really do have face coverings in shops, for instance, where there is a risk of transmission.”
Mr Johnson said he wanted people to go back to work “if they can” as he expressed a desire for people to “lead their lives more normally”.
He said: “I think everybody has sort of taken the ‘stay at home if you can’ – I think we should now say, well, ‘go back to work if you can’. Because I think it’s very important that people should try to lead their lives more normally.
“I want to see more people feeling confident to use the shops, use the restaurants, and get back into work – but only if we all follow the guidance.”
Face coverings are currently compulsory on public transport and in hospitals in England, but are only advised in other enclosed public spaces where social distancing is not possible and where “you will come into contact with people you do not normally meet”.
In Scotland, people are now legally obliged to wear face coverings inside shops and on public transport.
Shadow health secretary Jonathan Ashworth urged the Government to “conclude this review rapidly to provide the strong and clear guidance needed”.
Welsh First Minister Mark Drakeford said he did not think the evidence on wearing face coverings was “decisive” yet.
“I agree that as time goes on there is more emerging on the side of supporting face coverings in public.
“But I don’t think it is decisive yet. When the debate reaches a point, if it does, when the advice changes then the position will change in Wales.”
The latest figures from the Office for National Statistics suggested more than half (52%) of adults in Britain who left their home in the week before being surveyed had worn a face covering.
The survey was conducted between July 2-5 and is up from the previous week, when 43% reported doing so.
Tory former health secretary Jeremy Hunt said people should wear face coverings in shops, as he called for simple Government messaging.
The chairman of the Commons Health and Social Care Committee told BBC Radio 4’s Today programme: “I’m afraid I do go all ‘nanny’ on that one.
“I understand the public health advice, which is that if there’s a risk of being less than two metres close to someone then you should wear it but if not you don’t have to.
“But it doesn’t answer the basic question which is ‘if I’m going shopping, should I wear a face mask or not?’
“And I think with public health advice in a pandemic you just need simplicity, so I would favour saying we should wear face masks in shops.”
Earlier this week, the World Health Organisation acknowledged there is “emerging evidence” that Covid-19 could be spread through particles in the air.
And the president of the Royal Society, Professor Venki Ramakrishnan, said everyone should wear a face covering in public to reduce the risk of a second wave of Covid-19 infection.