England Chief Medical Officer Professor Chris Whitty said increasing rates of infection in the South East were “concerning” and encouraged people to stick to the guidance.
It comes as leaders in Greater Manchester are arguing for a move to Tier 2 next week as cases here have fallen – when the government reviews the Tiers next Wednesday.
London and parts of the South East, meanwhile, risk going into Tier 3.
Prof Whitty said a third wave is not inevitable but insisted people must be “very, very sensible” over the Christmas period.
Health Secretary Matt Hancock said he was “particularly concerned” about the number of cases in London, Kent and Essex, and that the data showed “by far” the fastest rise was among 11 to 18-year-olds.
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He told a Downing Street briefing on Thursday: “We need to do everything we can to stop the spread among school-age children in London right now – we must not wait until the review, which will take place on December 16. We need to take targeted action immediately.”
Speaking at his weekly press conference, Greater Manchester Mayor Andy Burnham urged ministers to give Greater Manchester the same ‘wider consideration’ given to the capital on the impact on jobs.
He said: “If you were to keep cities like Manchester in Tier 3 over the holiday period, it does have the effect, if hospitality is closed, of creating an incentive for people to have more informal gatherings in the home.
“We’re looking to the government for an evidence-based, balanced, wide consideration taking into account that people here have been living under restrictions for a number of months.”
Mr Burnham has called for the 10 boroughs to move out of Tier 2 as one, but said that splitting Greater Manchester into two different tiers could work.
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