UK health minister Sajid Javid won't rule out new Covid restrictions before Christmas

Britain reported a surge in cases of the Omicron coronavirus variant on Saturday, which government advisors said could be just the tip of the iceberg. London's mayor declared a "major incident" to help the city's hospitals cope.

Asked whether he could rule out restrictions before Christmas, Javid told BBC Television: "We are assessing the situation, it is very fast moving."

"There are no guarantees in this pandemic I don't think. At this point, we just have to keep everything under review."

Javid said the government was taking the "sobering" advice of its scientists seriously, was watching the data on an "almost hourly basis" and would balance that against the broader impact of restrictions on things such as businesses and education.

He said that there was a still a lot that is not known about Omicron but waiting until data is clearer may leave it too late to react to it.

The number of Omicron cases recorded across the UK hit almost 25,000 by Friday evening, up by more than 10,000 cases from 24 hours earlier, the UK Health Security Agency said.

The number of all new Covid-19 cases reported in official data on Saturday was 90,418. Cases were up 44.4pc over the seven days to December 18 compared with the previous week.

Javid said the government believed around 60pc of new Covid-19 cases in England were now Omicron.

London Mayor Sadiq Khan said he thought new restrictions were inevitable otherwise the health service would be on the verge of collapse under the joint pressures of staff shortages and increased hospitalisations.