Michael Gove has not ruled out the whole of England being moved into Tier 4 restrictions, saying it has to be “a judgment based on the medical situation”.
Hospitals in the south of England have seen a “real rise in pressure” as the number of coronavirus patients receiving treatment heads towards the April peak.
Paramedics in the capital are receiving almost 8,000 call-outs daily, and Boxing Day was described as one of London Ambulance Service’s “busiest ever days”.
Gove told BBC Breakfast: “We review which tiers parts of the country should be in on the basis of scientific evidence.
“The Joint Biosecurity Centre (JBC) will be making a recommendation to ministers, but I can’t pre-empt that because it obviously has to be a judgment based on the medical situation.
“As you quite rightly point out, the NHS is under pressure and these are difficult months ahead.”
A formal review of England’s tier system is due on 30 December but tier 4 restrictions for large parts of the country were introduced early last week due to concerns over the spread of a new more infectious strain of the virus.
Infection rates in England are currently highest in areas of Essex, London and other parts of the South East.
Brentwood in Essex has the highest rate in England, with 1,111 new cases recorded in the seven days to December 23 – the equivalent of 1,442.5 cases per 100,000 people.
The area is in Tier 4 of Covid-19 restrictions along with most of the south of the country, with socialising banned and people told to stay home.
There are concerns that socialising over the Christmas period may have helped the spread of the virus to other parts of the country.
Cases of the variant infection have been identified in more than a dozen countries with the latest reported in Norway, Madeira and Jordan.