Instead, they are suggesting imposing restrictions until everyone has had a chance to have their booster vaccination, plus an additional two weeks to allow immunity to build.

That would mean restrictions are in place until the second half of January at the earliest.

While Sage is an advisory body, its new advice is likely to place Boris Johnson and his ministers under pressure given they have previously suggested that preventing the NHS from becoming overwhelmed is the single most important criterion when deciding whether or not to lock down.

It is understood that the unusual release of Sage documents on a Saturday was done with Number 10’s blessing.

Minutes from last Thursday’s meeting include a scenario of “measures equivalent to those in place after Step 2 or Step 1 of the Roadmap in England”, a time when indoor mixing between households was banned.

“The earlier interventions happen the greater the effect they will have. This may also mean that they can be kept in place for a shorter duration,” the minutes say.

Meanwhile the Scientific Pandemic Influenza Group on Modelling, Operational sub-group (SPI-M-O), said in documents dated December 8 that in almost all modelling “a significant reduction in transmission (similar in scale to the national lockdown implemented in January 2021 and the pingdemic” in July 2021) is required to keep hospitalisations below the height of previous peaks”.

Cases doubling every two days

Sage adds that lateral flow tests should also be used on a group basis – so if one person in a group tests positive before going to an event, their whole group should also not attend, even if they did not test positive.

Figures indicate that cases of omicron are doubling every two days, with “hundreds of thousands” of new infections a day.

Experts are concerned about “immune escape” with indications that people face an eight to nine per cent chance of reinfection with omicron, compared to one per cent with Delta.

Sage believes that the variant has a three-fold increased risk of transmission within households compared to delta.

It is too early to assess omicron’s severity compared to previous variants, but the Sage minutes point out that early signals from South Africa, the origin of the outbreak, that it causes milder disease may have been misleading.

More reliable UK-based analysis should start to become available in the next week.