The threat of Christmas Covid restrictions is looming after Boris Johnson refused to rule out imposing more rules by December 25.
The Prime Minister declined three times to deny he could impose new limits in England in the next 12 days.
In Scotland, the nation’s Health Secretary said stricter rules are "inevitable" due to the spread of the Omicron variant north of the border.
First Minister Nicola Sturgeon is expected to make a Covid statement to the Scottish Parliament on Tuesday.
Mr Johnson was quizzed by broadcasters after warning a “tidal wave” of the variant, cases of which are doubling every two to three days, is on the way.
MPs have not even voted yet on face mask laws that took effect on Friday, or plans to force some venues to demand punters’ Covid passes from Wednesday.
But asked if more restrictions are on the way before December 25, Mr Johnson said “there are still some important things we don’t know”.
Last year the PM cancelled families’ Christmas plans on December 19, the day after the No10 Christmas party.
Asked if he could do that again, he said: "Throughout the pandemic I've been at great pains to stress to the public that we have to watch where the pandemic is going and we take whatever steps are necessary to protect public health.
"We think the steps that we are taking - so Plan B, combined with a hugely ambitious acceleration of the booster campaign, bringing it forward by a month so we offer a booster to every adult by the end of the year - we think that's the right approach."
Asked a third time to clarify he could not give a guarantee, he replied: “What I can tell you is we think that looking at the balance of the risks… the epidemiology… where we are with Omicron, everything we know - don’t forget, there are still some important things we don’t know about Omicron - we think this is the best approach.
“A combination of Plan B, which is some sensible steps to slow the spread of the virus to buy us some time to help to reduce the infections and of course the mortality rate.
“And then combine that with rapidly building up our booster defences.”
England’s officials have reportedly been drawing up a so-called 'Plan C' - and an even more draconian 'Plan D’.
Neither exist officially, but they could bring back Covid pass checking-in at pubs and restaurants, or even force hospitality firms to only serve outdoors, according to claims.
Scotland's Health Secretary Humza Yousaf said additional curbs were likely to be announced on Tuesday as the country battles with the new strain.
Mr Yousaf said Boris Johnson's target to offer boosters to all adults by the New Year will be "extremely challenging" and the Scottish Government would be requesting military help.
Asked about more restrictions in response to the Omicron outbreak, he told the BBC's Good Morning Scotland programme: "I think it's inevitable that we will announce additional protective measures."
Changes to the current coronavirus rules will be announced at Holyrood on Tuesday, Mr Yousaf added.
It came as the Prime Minister told broadcasters at least one patient has died with the Omicron Covid strain.
And hours earlier the government confirmed there were 10 patients with the new Omicron variant in England's hospitals.
Speculation has been continuing about whether Omicron is less lethal than the Delta variant. But shock data has shown Omicron cases doubling every two to three days - suggesting even if it is less lethal, it could still overwhelm the NHS.
Last night the PM warned of a "tidal wave" and announced routine appointments would be scrapped in a bid to give a million booster jabs every day between today and New Year's Eve. Huge queues formed at vaccine walk-in centres this morning, the booking website crashed and lateral flow tests ran out until tomorrow.
At the same time work-from-home guidance in England began today, and Mr Johnson faces a mass Tory revolt tomorrow over plans to force England's nightclub and event punters to show Covid passes from 6am on Wednesday.
