Boris Johnson says he thinks people should wear face coverings in shops - and will decide whether to make them mandatory in the coming days.
The Prime Minister indicated the government was looking at toughening up rules for wearing masks in shops on Friday.
And today he went further, saying a decision was coming “in the next few days.”
"They have a great deal of value in confined spaces where you're coming into contact with people you don't normally meet," the Prime Minister told reporters during a visit to the London Ambulance Service.
"The scientific evaluation of face coverings and their importance on stopping aerosol droplets, that's been growing, so I do think that in shops it is very important to wear a face covering if you're going to be in a confined space and you want to protect other people and receive protection in turn."
He added: "Yes, face coverings, I think people should be wearing in shops, and in terms of how we do that - whether we will be making that mandatory or not - we will be looking at the guidance, we will be saying a little bit more in the next few days."
Over the weekend, Cabinet Office Minister Michael Gove said it should be voluntary.
Labour has called on Mr Johnson to make face coverings compulsory in shops in England – as they are on public transport.
Shadow Cabinet Office Minister Rachel Reeves told the BBC: “I think that would be a sensible way forward. People are increasingly wearing them but greater clarity from Government about that would be helpful.
“People want to do the right thing but they want to know what the right thing is.
“I think it would inspire greater confidence and might encourage more people to go out and spend money if they see more people wearing face masks in shops.”
Mr Gove stopped short of saying they should be compulsory, but claimed good manners meant masks should be worn.
He said: “I would encourage people to wear face masks when they’re inside in an environment where they’re likely to be mixing with others and where the ventilation may not be as good as it might.
“I think that it is basic good manners, courtesy, consideration to wear a face mask if you are, for example, in a shop.”