Face masks should be mandatory in shops and other confined public spaces, the Mayor of London has said.
Sadiq Khan wrote to Prime Minister Boris Johnson, urging him to introduce a new law as soon as possible.
Face coverings are already mandatory on public transport in England – but though the Government has advised wearing them in shops since mid-May, it is not compulsory.
But the Mayor said face masks will play a “key role” to slow the spread of coronavirus as lockdown restrictions ease, and Londoners must not be “complacent”.
It comes after high street shops began to reopen on Monday (14 June), with long queues at Primark, Nike and other popular brands.
While face masks may not prevent the wearer from catching coronavirus, emerging scientific evidence suggests they can stop people from passing it on to others.
Anyone with Covid-19 symptoms must self-isolate at home for seven days – but some people show no symptoms when they have the disease, and can still spread it.
Face masks have been compulsory on trains and buses in England since Monday, with Transport for London (TfL) reporting between 80% and 90% compliance on the Tube on the first day.
But the World Health Organisation now says face coverings should also be worn in shops.
Several European nations, including Austria, France, Germany, Portugal and Spain have already introduced the rule.
The Mayor said Londoners have shown they are willing to wear face masks on public transport – and that law should now be extended to other high risk public spaces.
“As restrictions are eased it is vital that we do not become complacent and that we all continue to do everything we can to prevent a devastating second wave,” he said.
“It is increasingly clear that face coverings will play a key role in our efforts to stop the further spread of the virus and they need to become a more regular part of our day-to-day life.”