Tough new Covid restrictions would come in next week and last until the spring, under one scenario which has been modelled for government scientists.

Papers released by the Scientific Advisory Group for Emergencies (Sage) included University of Warwick modelling looking at tighter rules starting on December 28 or New Year’s Day and lasting until January 15, January 28 or March 28.

The latest of those dates, if it was adopted by Boris Johnson, would mean England going back into tighter restrictions for three months after Christmas. It is longer than publicly suggested by some of the most cautious scientists and politicians.

A Downing Street source played down the possibility of that option being implemented, however, stressing that the modelling has not been submitted to government ministers yet for consideration.

However, the fact that government scientists are discussing the idea reflects how seriously the surge of the omicron variant of Covid-19 is being treated as they consider what to advise.

Changes in Covid restrictions only come into effect once the Prime Minister and his Cabinet agree what action to take and Parliament has voted through any legal changes.

Proposals could pile pressure on Cabinet

The modelling came as two government scientists defended their analysis of the threat posed by omicron, dismissing critics who have dubbed scientific warnings “doomsday” scenarios.

Dr Jenny Harries, the chief executive of the UK Health Security Agency, insisted that omicron remains a “serious threat” despite new encouraging data about the variant, while Sir Patrick Vallance, the Government’s Chief Scientific Adviser, defended scientific models after criticism from Tory MPs.

The release of the modelling on Christmas Eve could heap pressure on the Cabinet, which is expected to meet early next week, to consider the possibility of new restrictions given the omicon surge.

The new statement from the Scientific Pandemic Influenza Group on Modelling (Spi-M), a government advisory group which sits alongside Sage, was published online on Christmas Eve.

The Spi-M statement made reference to modelling conducted by the University of Warwick, which was also published separately and considers possible options for tightening the rules.

The road back to step two?

The intervention which was considered is returning to step two of the Government’s reopening roadmap, as was followed in the first half of 2021.

During step two, indoor socialising was not allowed outside your own household or support bubble, but outdoor socialising was allowed in a group of up to six people.

Pubs, bars and restaurants were closed indoors but could serve people outdoors, while working from home was encouraged. Hotels and hostels were closed.

The analysis looked at the impact of adopting the new rules on December 28, two days after Boxing Day, and January 1.

It also considered them ending with a return to Plan B restrictions, the current rules in England, on January 15, January 28 or March 28.