Boris Johnson has said people in England “should be wearing” face coverings inside shops to help prevent the spread of coronavirus.
The prime minister said the government would decide in the next few days if “tools of enforcement” were needed.
The comments follow cabinet minister Michael Gove telling the BBC on Sunday that coverings should not become mandatory in shops in England.
Labour has demanded “urgent clarity” from the government on the issue.
And the boss of Waterstones bookstores, James Daunt, said it “would not be right” to ask shop workers to “police” any new policy.