From Saturday, 68% of England's population will be in Tier 3 and 30% in Tier 2.
Large areas of England will be added to the 'very high alert' Covid-19 category this weekend, placing residents under the most stringent set of restrictions to tackle a rising number of infections.
Britain, like other countries, is struggling to tame a second wave of novel coronavirus cases and deaths, and the government is having to defend a plan to relax contact restrictions for five days over Christmas.
In a sign of mounting anxiety over the potential consequences of Christmas socialising, the government said most secondary school pupils would have a week of remote learning before returning to classrooms in January.
Health minister Matt Hancock said cases in the southeast of England were up by 46% in the last week, while hospital admissions were up by more than a third. In eastern England, cases were up by two-thirds, and hospital admissions by nearly half.
"It is therefore necessary to apply Tier 3 measures across a much wider area of the east and southeast of England," he told parliament, referring to the strictest of three levels of Covid-related restrictions being applied in England.
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New measures will take effect from Saturday
He said the new measures would be in force from Saturday. A small number of areas had their restrictions eased.
London was placed into Tier 3 this week after an emergency review identified a surge in infections.
The changes mean that from Saturday, 68% of England's population will be in Tier 3 and 30% in Tier 2.
Fewer than a million people will be in the more relaxed Tier 1.
In Tier 2, bars are shut and households are banned from mixing to socialise indoors. Tier 3 also shuts dine-in restaurants, hotels, theatres and cinemas, and places more rules on socialising and travel. Shops, workplaces and schools mostly stay open in all tiers.
Under the new plans for secondary schools announced on Thursday, most pupils will spend the first week of the new term in January at home, learning remotely until Jan. 11. Only those in exam years, those considered vulnerable and the children of critical workers will be allowed back to school on January 4.
The education ministry said the delayed return, paired with a programme of free testing for pupils and school staff, would "help to deliver the national priority to keep education open for all and help fight the spread of the virus".
The government has allowed family members to travel to visit relatives over Christmas, but is now urging people to keep their celebrations small and local.
The semi-autonomous governments of the other nations of the United Kingdom - Scotland , Wales and Northern Ireland - each set their own public health policies,
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