Prime Minister Boris Johnson's government has also brought in new rules for England to slow the spread of Omicron with orders for people to work at home if possible, wear masks in public and for entertainment venues to use vaccine passports.
Britain reported 58,194 new cases in 24 hours, the highest daily total since January. Health officials say Omicron is now in the community and there could be more than one million infections by the end of the month.
The UK Health Security Agency said that there was no data to assess the severity of Omicron, despite the fact that no cases of Omicron had yet to result in hospitalization or death.
The report by London School of Hygiene Tropical Medicine LSHTM, which has not been peer reviewed, suggested that there would be more than 2,000 daily hospitalisations and 24,700 deaths between December 1 and April 30 if no further action is taken by the government.
The hospital admissions of patients would be twice as high as in January this year, with about 492,000 hospital admissions and 74,800 deaths, according to the most pessimistic modelling.
The impact of Omicron would be reduced in the early part of 2022 with mild control measures such as working from home, said Rosanna Barnard, head of the school's Centre for the Mathematical Modelling of Infectious Diseases.
Our most pessimistic scenario suggests that we may have to endure more stringent restrictions to make sure the NHS National Health Service is not overwhelmed. Mask-wearing, social distancing and booster jabs are vital but may not be enough. Johnson, who is facing significant opposition from within his Conservative party over the latest restrictions, is not planning to go beyond Plan B measures, his spokesman said on Friday.
The government hopes that an accelerated rollout of booster vaccine doses, which early data suggests restore protection against mild disease caused by the Omicron variant, will reduce the need for new controls.