Hertfordshire's police force says it is waiting for "formal guidance" over enforcing a new law for shoppers to wear face coverings in England.

The government is making it mandatory for people to wear a face mask in shops and supermarkets across the country from Friday in a bid to stop the spread of Covid-19.

Hertfordshire Constabulary hopes that the rules will be followed by people in the county "as a joint effort between the retail sector, customers, government and police", although says it is waiting for more details on enforcing the new law.

It said in a statement: "While we await formal guidance, the National Police Chiefs’ Council is working closely with the Home Office, retailers and trade bodies ahead of implementation, and has indicated that retailers will manage entry to their stores and compliance with the law while customers are inside, with police involvement as a last resort.

"As with other coronavirus regulations, Hertfordshire Constabulary will follow an approach of engaging, explaining, encouraging and only enforcing where encouragement has been unsuccessful.

"The vast majority of people are complying with the regulations to manage the spread of Covid-19 and hopefully this will continue as a joint effort between the retail sector, customers, government and police."

Health Secretary Matt Hancock told MPs that face coverings would help give people "more confidence to shop safely" and help protect staff.

He said: "Should an individual without an exemption refuse to wear a face covering, a shop can refuse them entry and can call the police if people refuse to comply.

"The police have formal enforcement powers and can issue a fine."

The government warned that those who fail to comply with the law would face a fine of up to £100.