Health Minister Sajid Javid said face masks will be mandatory in shops and on public transport in England from Tuesday in response to the new Omicron variant.
This brings England in line with other parts of the UK. The prime minister also announced earlier that PCR tests would be required for all overseas arrivals.
Arrivals from 10 new red list countries will have to be quarantined for 10 days.
MPs must vote on the confirmation of the measures after it takes effect.
The government has stopped extending vaccine passports in England and issuing advice to work from home, which is part of its Plan B – a contingency plan if intervention on Covid is needed to protect the NHS.
Mr Javid told Sky News the actions taken were “proportionate and balanced”, and he hoped they could be lifted “within weeks”.
He told the Trevor Phillips on Sunday program that it would be “irresponsible” to make guarantees over Christmas, but said people should continue with their plans.
“I think it’s going to be a wonderful Christmas,” he said.
The health secretary said stricter rules on testing for overseas arrivals would be implemented “as soon as possible” with the agreement of the UK’s four nations.
But Mr Javid said the country was “nowhere near” to reintroduce measures such as working from home or social distance, arguing that it had a “heavy price” economically, socially and in terms of mental health .
He added that he expected the government’s vaccine advisers to advise him “threateningly” on extending the stimulus program to younger age groups.
At a news conference in Downing Street on Saturday, the prime minister called the new measures temporary and precautionary – saying it would be reviewed in three weeks, just before most schools break up for the Christmas holidays.
Labor called for the full implementation of Plan B and for improved sick pay to encourage self-isolation.
Boris Johnson announced the restrictions after it was confirmed that two Omicron cases had been detected in Brentwood, Essex and Nottingham. Officials said the cases were linked and linked to travel in Southern Africa, where the new variant was first identified.
Mr Johnson said: “We need to slow down the spread of this variant here in the UK because measures at the border can only minimize and delay the arrival of a new variant rather than stopping it all together.”