Downing Street sources insisted “no decisions have been made”, but there is widespread speculation that further measures could be imminent.
And the Covid-O subcommittee of experts is understood to be holding a meeting later on Wednesday.
A prominent member of the Scientific Advisory Group for Emergencies (Sage) warned that a full UK-wide lockdown to deal with the threat of the Omicron variant cannot be ruled out, although the current threat posed by the strain remains unclear.
Any move to impose fresh restrictions would be viewed with suspicion in Westminster at a time when Boris Johnson is under pressure over allegations No. 10 staff breached lockdown rules by holding a Christmas party last December.
Footage emerged on Tuesday night of senior aides joking about the party just days after it reportedly occurred in the run-up to Christmas 2020 and Mr Johnson is braced for the issue to feature prominently at Prime Minister’s Questions.
The UK Government has so far insisted it is not time to activate its Plan B – the restrictions that would be brought in to prevent the NHS being overwhelmed this winter.
But Omicron may have changed those calculations in Downing Street, with Mr Johnson telling the Cabinet on Tuesday that “early indications were that it was more transmissible” than the Delta strain.
Restrictions could play a role in slowing the spread of the variant in order to allow more time for the booster jab vaccination campaign to progress.
Sage member Professor Neil Ferguson, from Imperial College London, whose data was instrumental to the UK going into lockdown in March 2020, said the variant is concerning but it is still unknown what its impact will be on severe disease.
He suggested people may be told to work from home in the near future as Omicron is spreading fast, with the variant set to take over from the Delta strain before Christmas.
Speaking in a personal capacity, he told BBC Radio 4’s Today programme: “Certainly case numbers of Omicron are doubling at least every three days, maybe even every two days at the moment, so it’s accelerating very fast and, (to) put that in context, it’s the same if not faster than we saw with the original strain of the virus in March of last year. So it is a concern.
“It’s likely to overtake Delta before Christmas at this rate – precisely when is hard to say.
“We’ll start seeing an impact on overall case numbers – it’s still probably only 2%, 3% of all cases so it’s kind of swamped, but within a week or two, we’ll start seeing overall case numbers accelerate quite markedly as well.”
Prof Ferguson said the peak of this wave of infection will be in January if no measures are taken to slow it down.
“So if you don’t do anything at the current time, it will most likely be some time in January,” he said.
“But I think the key question is whether the country decides to adopt measures to either slow it down or try to stop it, and that will critically depend on really the threat it poses in terms of hospitalisations.
“At the moment, we don’t really have a good handle on the severity of this virus; there’s a little hint in the UK data that infections are a little bit more likely to be asymptomatic, but we really need to firm up that evidence at the current time.”
Asked whether people should be told to work from home, he said: “It will be up to the Government to decide what to announce in the coming days and weeks.
“There is a rationale, just epidemiologically, to try and slow this down, to buy us more time principally to get boosters into people’s arms, because we do think people who are boosted will have the best level of protection possible, but also to buy us more time to really better characterise the threat.
“So, if you imagine a kind of Plan B Plus with working from home might slow it down – it wouldn’t stop it, but it could slow it down, so it’s doubling rather than every two or three days, every five or six days.
“That doesn’t seem like a lot, but it actually is potentially a lot in terms of allowing us to characterise this virus better and boost population immunity.”
Regarding lockdowns, Prof Ferguson said it is very difficult to rule out anything, adding that we “haven’t got a good enough handle on the threat”.
He added: “Clearly, if the consensus is it is highly likely that the NHS is going to be overwhelmed then it will be for the Government to decide what what he wants to do about that, but it’s a difficult situation to be in, of course.”
Pushed on whether lockdowns might be possible, he said: “It certainly might be possible at the current time.”