Boris Johnson has been urged to make it mandatory for shoppers to wear face coverings.

London Mayor Sadiq Khan wrote to the Prime Minister calling for the change, arguing that the measure was supported by scientific studies and had already been adopted in countries across Europe.

Non-essential shops in England were given permission to open on Monday and further easing of the lockdown is expected next month, with bars and restaurants hoping to welcome customers from July 4.

In his letter to the Prime Minister, Mr Khan said face coverings should be mandatory in “busy public settings” including shops.

“The World Health Organisation updated its guidance to recommend the use of face coverings in a wide range of public settings, including grocery stores, and many European countries – whose lead we have often later followed – have mandated their use in shops and other confined public spaces as part of their strategy for reopening, including Austria, France, German, Portugal and Spain.”

Face coverings are already mandatory on public transport in England and protection is also compulsory for hospital staff and visitors.

The London Mayor 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.

“The high level of use on our public transport network has again shown that Londoners are willing to act to protect their community, but the Government’s current rules are lagging behind other countries.

“With non-essential shops now opening and the public returning to our high streets, I urge the Government to follow World Health Organisation guidance and make these coverings mandatory for those shopping in retail outlets and in other spaces where it is impossible to keep a safe distance.”