Troops could be drafted in to help crucial public services left stricken by Covid staff shortages.
All Whitehall departments have been asked to draw up contingency plans for up to a quarter of their staff isolating at the same time.
Now it has emerged that for some departments, related to critical infrastructure or supply chains, that could involve formally requesting troops under the Military Aid to the Civil Authorities (MACA) system.
Boris Johnson ’s official spokesman said today: “All departments have been asked to look at how they would mitigate against large scale absences across their relevant workforces up to 25%.
“In some circumstances that might require making a MACA, a Military Aid request. In other circumstances it might not.
“There’s no blanket requirement for military aid.”
Soldiers have already been helping with the vaccine rollout.
Brits are still advised to work from home to tackle the surge of the Omicron variant.
But those workplaces that have to be in-person were meant to return to full strength today for the first time since Christmas.
Absences were expected to surge after more than 218,000 people tested positive for Covid in the UK on December 29.
The number of hospital workers absent due to the virus soared by 31% in a week. A total of 24,632 staff members were off on Boxing Day, compared with 18,829 a week earlier.
A senior government source told The Times: “The virus is spreading very quickly so different regions could be hit at the same time, so their capacity to offer mutual aid will be impacted.
“So departments have been tasked to look at their plans afresh in light of different characteristics of previous strings of virus."
Boris Johnson will hold a crunch Cabinet meeting tomorrow morning on Covid rules as England’s restrictions face an official review.
But the chance of any new restrictions this week appear slim to nil after a Tory minister today insisted “Plan B is working”.
At least half a dozen NHS trusts have declared critical incidents as thousands of health staff isolate due to the Omicron variant.
But the PM's spokesman said today: “At the moment we don’t see any data to suggest further restrictions would be the right approach.”
Boris Johnson is expected to give a Downing Street press conference at 5pm today after being briefed on the data.
He or Health Secretary Sajid Javid will then formally update MPs at around 4pm tomorrow, the day England’s Covid rules are officially reviewed. Mr Johnson will hold the first PMQs since Christmas at the later time of 3pm tomorrow.
Plan B in England involves advising people to work from home, ordering masks on public transport and shops, and forcing punters at nightclubs and other venues to prove they’ve had a vaccine or negative test.
Vaccines Minister Maggie Throup insisted Plan B "is working", pointing to figures showing fewer Covid-19 patients are in hospital compared with last year.
She said: “The Prime Minister has said that Plan B is working… and I don’t see any reason why we need to change.
“It’s important we do follow the data, we’ve done that all along and we’ll continue to do that.”
Over 14,000 patients are in hospital with Covid in England, double the rate on Christmas Day though less than the 25,000 this time last year.
Yet No10 said today: "There’s clearly evidence that [Omicron] does appear to be a milder disease than what came before... There are various studies on that which differ slightly on exactly how much."
NHS Confederation chief executive Matthew Taylor said hospital admissions seemed to have "perhaps plateaued in London”.
But he added “it's rising across the rest of Britain" and for many hospitals, "the most pressing element of all" was staff absences.
He also slammed a “politicised attempt” to downplay the scale of the problem in hospitals.
Mr Taylor told Times Radio: “We've got to recognise in the next few weeks at least, things are very, very difficult.
“And I think that one thing that people in the health service find difficult is it does seem as though there's a kind of almost politicised attempt to suggest that things aren't as difficult as they are.”
