Wearing a face covering whilst visiting shops in England is to become compulsory from July 24, the government is set to announce.
Those who fail to comply with the new rules will face a fine of up to £100, which will be enforced by the police.
Retail staff will be exempt from the new mandatory rule but will be expected to encourage the policy.
There has been mounting pressure on the Prime Minister to make a decision following confusion over whether the new rule should come into force amid evidence that masks can hinder the transmission of the virus. Face coverings were made mandatory on public transport on June 15.
There is also rising concerns over the risk of coronavirus spreading over the next 10 days until the new rule is officially introduced.
On Friday, face coverings became compulsory in shops and supermarkets in Scotland.
The move from the Prime Minister will also bring England in line with other major European countries such as Spain, Italy and Germany.
From July 27, three-layer face coverings will be made mandatory on public transport in Wales and on Friday in Northern Ireland masks became compulsory on public transport. Both measures are said to be under review.
Since mid-May, the public have been advised to wear coverings in enclosed public spaces, where they may encounter people they would not usually meet.
A YouGov poll found that 36% of people in the UK wear a face mask in public places, compared with 86% in Spain, 83% in Italy, 78% in France and 65% in Germany.
Paddy Lillis, general secretary of trade union Usdaw, commented: “It is right to make the wearing of face coverings mandatory in shops, but we must recognise that expert advice says it is an additional protection on top of existing safety measures. There now must be clear and detailed guidance from the Government and we urge them to work with Usdaw and retail employers to draw that up, as we successfully did on joint safety guidance for the reopening of high street retail with the British Retail Consortium.
“Usdaw is urging employers to stay with the established two-metre social distancing, using screens at tills and limiting the number of shoppers in store at any one time. Employers must also be aware that staff will need regular breaks when they can take their face covering off and have the opportunity to replace it. Staff on tills who are behind screens should not be required to wear a face covering.
“We welcome the indication that shop workers will not be expected to enforce the wearing of face coverings. They are already dealing with more abuse than normal and this could be another flashpoint. There must also be clarity on age identification procedures, under the ‘Think-25’ policy, when a customer is wearing a face covering.
“We now need a public information campaign to explain the correct use of face coverings, that some people are exempt from wearing face coverings and the importance of maintaining existing social distancing and hygiene measures.”