Wearing a face covering whilst visiting shops in England became compulsory from July 24.
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.
It comes after 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.
As the rules became mandatory and police could issue fines, mobility retailers, like supermarkets and clothes shops, will have to ensure customers browsing in-store have their faces covered up.
Those who do not comply with the rules can face a fine of up to £100 but, despite the blanket rule, there are some people who are exempt from the fines and do not have to wear a covering.
Government explained that in some cases, such as for health or age reasons, people will not be required to cover faces.
This can include reasons related to risk, mental or physical illness or because of age.
Responding to decision to make face coverings mandatory in shops in England from July 24, Helen Dickinson, chief executive of the British Retail Consortium, said although retailers will play their part, they should not have to enforce the rules.
Dickinson explains: “Retailers have made the safety of staff and customers their top priority and we support measures aimed at protecting the health of the public.
“While retailers will play their part in communicating the new rules on face coverings, they must not be the ones enforcing these rules. With hundreds of incidents of violence and abuse directed at retail staff every day, we welcome the announcement that enforcement will be left to the authorities, rather than potentially putting hardworking retail colleagues in harm’s way.”
She continued: “We look forward to further clarity over whether the wearing of face coverings will apply to shop staff. If so, there must be flexibility for colleagues who are in stores all day and can already benefit from other safety measures such as protective screens and 2m distancing.”
Adding: “Retailers have already spent hundreds of millions installing perspex screens, implementing social distancing measures and providing additional cleaning in stores; we hope this announcement will make shoppers feel even more confident about returning to the high street.