Masks will become compulsory in shops and on public transport from Tuesday, health secretary Sajid Javid has confirmed.

Prime minister Boris Johnson announced the reintroduction of the rules at a press conference on Saturday - amid concerns over the new Omicron variant of Covid-19.

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And on Sunday morning, health secretary Mr Javid confirmed it would be Tuesday when masks would be compulsory in shops and on public transport. Hospitality is exempt.

Mr Javid said: "Doing it in this proportionate way where it's for public transport, it's for retail outlets, I think is the right level of response on masks.

"It will be via government regulation and that means, I think, that people will take it seriously."

Pressed on whether people will following the rules on masks, Mr Javid said following the news of a new variant: "I do think people will take this more seriously."

He added: "I hope this is something that we can remove within weeks. But I do think in terms of making progress, we want life to go back towards normal, but at this point in time, given what we know about this variant, and the expert advice that has been received, I think it is right to take some proportionate and balanced action."

The prime minister had announced the strengthening of England's rules after cases of the variant, first identified in parts of southern Africa, were found in Nottingham and Brentwood in Essex.

Both were linked to travel to southern Africa and testing has been ramped in those areas.

Mr Johnson announced the return of mask wearing among "temporary and precautionary" measures to be reviewed in three weeks, alongside a "boost" to the booster campaign.

All new international arrivals to the UK will have to take a PCR test on the second day and quarantine until they test negative for coronavirus, while all contacts of confirmed Omicron cases will have to self-isolate for 10 days.

Duncan Baker, Conservative MP for North Norfolk, said the government was right to "err on the side of caution".

He said: "At this stage the risks are not fully known. But erring on the side of caution with the concern that Omicron may be more transmissible and evade the vaccines more, the government has quickly acted to ensure the new variant’s spread can be slowed.

"Within a short time, I am confident our scientists will soon understand more about the variant."

Scientists are not yet clear on whether the Omicron variant is more transmissible or how effective current vaccines are against it.

Mr Javid told the Sky News Trevor Phillips on Sunday programme he has been taking advice over whether the booster vaccination can be extended.

The Joint Committee on Vaccination and Immunisation (JCVI) has been tasked with looking at whether boosters can be extended down from the over-40s to the over-18s.

The experts will also consider whether second doses should be offered to 12 to 15-year-olds, and whether the current six-month wait before a booster jab could be reduced.

Mr Javid said "we're nowhere near" reintroducing working from home or social distancing measures to combat coronavirus.

He said: "We know now those types of measures do carry a very heavy price, both economically, socially, in terms of non-Covid health outcomes such as impact on mental health.

"So, if one was to make decisions like that they would have to be done very, very carefully and we're not there yet, we're nowhere near that."

He said people should plan for Christmas as "normal".

He said: "I think it's fair to say that the nature of this pandemic is it would be irresponsible to make guarantees.

"As for Christmas, I think people should continue with their plans as normal for Christmas, I think it's going to be a great Christmas."

Scientists in Norfolk who will hunt to track the spread of the new variant have said its emergence is "concerning".

Dr Andrew Page, from the Norwich Research Park-based Quadram Institute, said: "The Omicron variant is concerning because it has a very large number of mutations in the spike protein of the virus, and they could potentially make this new variant more transmissible or reduce the effectiveness of current vaccines.

"At the Quadram Institute, we will continue to hunt for new SARS-CoV-2 variants and to give the UK early warning of any emerging threats but, importantly, we can all help protect our communities by getting our vaccinations, limiting contact with other people, and wearing face masks in crowded places."

Dr Louise Smith, Norfolk's director of public health, has urged people to keep getting their vaccinations and booster jabs.