The Prime Minister said it is "very important" to wear a face covering in confined space "to protect other people and receive protection".
His comments came after Cabinet Office Minister Michael Gove said they should not be made compulsory, despite Mr Johnson calling for "stricter" rules. A behavioural expert who advises ministers said the messaging should be “clear, coherent and consistent”.
Meanwhile, beauty salons, nail bars and tattoo shops reopened on Monday for the first time in four months as part of the latest relaxation of lockdown restrictions in England.
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