Health Secretary Sajid Javid has said face masks will be compulsory in shops and on public transport in England from Tuesday in response to the new Omicron variant.
It brings England in line with other parts of the UK. The PM also announced earlier that PCR tests would be required for all overseas arrivals.
Arrivals from 10 new red list countries will need to quarantine for 10 days.
MPs are due to vote on confirming the measures after they come into force.
The government has stopped short of extending vaccine passports in England and issuing advice to work from home, which are 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 being taken were “proportionate and balanced”, and he hoped they could be lifted “within weeks”.
He told the Trevor Phillips on Sunday programme it would be “irresponsible” to make guarantees about Christmas, but said people should continue with their plans.
“I think it’s going to be a great Christmas,” he said.
The total number of confirmed cases in England is now 13.
The new cases include six in London – one each in Haringey, Sutton, Camden, and Westminster, and two in Barnet – and one in Liverpool, and one in north Norfolk.
The individuals who have tested positive, and their contacts, are all isolating, health officials said.
Well according to our First Minister, the Scottish cases all appear to have originated from a single private event taking place in or around the 20th November. So I’m really hoping these can be contained. I hope the cases down south fizzle out
The latest ONS figures show about one in 60 people in private households in England had Covid-19 in the week to November 27, up from one in 65 the previous week.
UK health minister Ed Argar accepted this winter will be “critical for our NHS”, but told MPs the government is doing “everything” it can to protect Britons through new Covid measures on mask wearing, border controls and the bolstered vaccination programme.
There are now dozens of cases of the variant in the UK now and the number of infections is expected to grow significantly in the coming days.
Health Secretary Sajid Javid told MPs the variant was continuing to spread “here and around the world” and there were now cases here “with no links to international travel”.
There have been 336 confirmed cases of the highly-mutated variant across the UK, he said, a rise of 90 from Sunday.
Of the confirmed Omicron cases, 261 were in England, 71 in Scotland and four in Wales - while Northern Ireland is yet to have a confirmed case. Mr Javid said that as far as he was aware none of those people had been admitted to hospital.
