Face coverings should be made mandatory in shops and confined public spaces, London's mayor has said.
Most people in England must wear them on public transport and in hospitals, while the government recommends their use when distancing is not possible.
In a letter to the prime minister, Sadiq Khan said the UK was "lagging behind other countries" as masks became "increasingly important" in fighting coronavirus.
The government has yet to comment.
However, the Greater London Authority (GLA) Conservatives said the government had "followed scientific advice on this issue and the mayor should wait for the next review of social distancing measures".
Current guidance from the World Health Organisation (WHO) states that non-medical face coverings should be worn in public where social distancing is not possible.
Mr Khan wrote that scientific evidence showed masks "can help slow the spread of the coronavirus".
Customers must wear face coverings in shops in several European countries including Austria, France, Germany, Portugal and Spain.
The mayor said Londoners had shown a willingness to wear masks, with a "high proportion of passengers" on public transport using them.
"With non-essential shops now opening and the public returning to our high streets, I urge the government to follow WHO guidance and make these coverings mandatory," he said.
In its guidance about coverings, the government's website states that "wearing a face covering does not protect you" although "if you are infected but have not yet developed symptoms, it may provide some protection for others".
Speaking about Mr Khan's letter, GLA Conservative health spokesman Andrew Boff said: "People are rightly advised to wear a face covering when they go shopping to help control the virus and it is now mandatory on public transport.
"Sadiq Khan should spend less time and resources lecturing the government and focus on enforcing the new rule on the Transport for London network, where worryingly some commuters are still travelling without a face covering."