The Financial Times reported that Boris Johnson was presented with a number of options on Friday under a so-called Plan C, ranging from "mild guidance to nudge people, right through to lockdown".
The newspaper quoted allies of the Prime Minister who claimed Mr Johnson still wanted to go down the guidance route, but that he also had to be realistic about the threat of Omicron.
And leaked minutes from the Scientific Advisory Group for Emergencies (Sage), seen by the BBC, said scientists had told ministers that tougher measures need to be brought in "very soon".
The BBC reported the advisers had recommended moving to restrictions seen in step one and two of the easing of lockdown restrictions in the spring. This included a ban on indoor mixing and indoor hospitality.
And they reportedly warned against delaying further interventions until 2022.
The Times reported that draft regulations were being prepared which could ban meeting others indoors except for work purposes, and that pubs and restaurants would be limited to outdoor service only, for two weeks after Christmas.
Lord Victor Adebowale, chairman of the NHS Confederation, voiced support for a circuit-breaker, warning that a cautionary approach should be taken.
He told Times Radio: "I would support the circuit-breaker. My members would support the circuit-breaker.
"We've been calling for Plan B for some time now and we're glad that it was voted through. I think the Government has to be prepared to recall Parliament if further interventions are needed."
He added: "The fact of the matter is we should be taking the precautionary principle. We should be protecting our NHS and our public services. We have no economy without health."
The UK reported more than 90,000 new Covid cases in another record daily total on Friday.
A Government spokesperson said: "The Government will continue to look closely at all the emerging data and we'll keep our measures under review as we learn more about this variant."
It comes after Rishi Sunak flew back from a work trip to California early for crisis talks with business leaders concerned about the impact of measures, especially on the hospitality sector.
The Chancellor met virtually with the Confederation of British Industry, the Federation of Small Businesses, and the British Chambers of Commerce on Friday afternoon.
The groups raised concerns about the impact of cancellations across hospitality in the run-up to Christmas, and the importance of clear messaging from the Government.
Meanwhile, the UK's devolved administrations have ramped up their demands for more financial support as Omicron cases continue to fuel infection rates.
A Cobra meeting is set to be held over the weekend with the leaders of the devolved nations.
Mr Johnson has warned Omicron is "a very serious threat to us now".
On a visit to a vaccination centre in Hillingdon, west London, on Friday, he said: "We are seeing a considerable wave coming through and people have got to be prepared and they have got to understand what it entails."
Asked about conflicting messages from the Government and its advisers on socialising over the Christmas break, Mr Johnson said: "What both Chris Whitty and I are saying is that there is a big wave of Omicron coming through.
"People need to be prudent. You need to think about your budget of risk."
According to the Government's latest figures, a further 93,045 lab-confirmed Covid-19 cases were recorded in the UK as of 9am on Friday, the highest daily total recorded since the pandemic began and a rise of 4,669 on the previous record set on Thursday.
The number of people in hospital with Covid-19 in London, which has seen some of the biggest rises in cases in the last seven days, has climbed to 1,534, up 28.6% on last week.
The Government's dashboard showed that 341 more people with Covid were in hospital in the capital on December 17, rising from 1,193 on December 10.
Across the UK, 7,611 people are in hospital with the virus, a rise of 163 patients (2%) on the previous week.