Prof Hayward, a professor of infectious disease epidemiology at University College London, said mixing at Christmas does pose "substantial risks" particularly where generations "with high incidence of infection" socialise with older people "who now have much lower levels of infection and are at most risk of dying" if they catch Covid-19.
The Professor of infectious disease epidemiology at the University College London (UCL) told BBC Radio 4's Today programme, "Mixing at Christmas does pose substantial risks, particularly in terms of bringing together generations with high incidence of infection with the older generations who now have much lower levels of infection and are at most risk of dying if they catch Covid".
'My personal view is we're putting far too much emphasis on having a near-normal Christmas, ' he told Radio 4's Today programme.
Boris Johnson was facing a battle to save Christmas last night after a Government adviser warned that allowing festive gatherings would "throw fuel on the fire" of the pandemic.
Respect the fact that we mustn’t spread the virus further’ Health secretary Matt Hancock
Public Health England (PHE) suggested earlier this week that for every one day restrictions were relaxed over the holiday, there would need to be an extra five days of tighter rules.
But the Sage assessment only considers the preliminary findings from unpublished modelling.
The government has said that families should be able to come together after a "difficult year" but ministers have so far resisted confirming plans to ease restrictions. The PM wants to reintroduce regional restrictions but it is not yet clear if the previous system will be reintroduced or if measures will be beefed up.
Epidemiologist John Edmunds, a member of Sage, said that the ban, which previously applied only in Tier Two and above, would have to be extended.
Mr Johnson is also expected to produce a UK-wide plan for Christmas after talks on what approach to take.More news: Danish minister resigns over mink virus row
Officials were unable to say if carol singing will be banned this year.
Downing Street declined to comment, but did not deny the report.
Speaking to LBC on Friday, she pointed out that officers had "no powers of entry" into Britons' homes if there are suspected breaches of coronavirus laws, continuing: "I have no intention anyway of encouraging my people to be barging through people's doors or knocking on people's doors, unless you've got, as we sometimes do, a huge party going on which is clearly very, very unsafe and causing lots of concern - for them, we might be knocking on doors, saying you need to stop this". Other minister, including health secretary Matt Hancock, have refused to say what will happen at the end of the lockdown.
Defence Secretary Ben Wallace said the Government wanted to see the impact of lockdown on the spread of the disease before finalising the plans.
When will a decision be made on ending the second lockdown? I'm not campaigning for that.More news: Kylie Cosmetics debuts Grinch-inspired collection, credits daughter Stormi for this idea
Inter-county travel in the south will also be permitted for a brief period to allow people go home to see friends and family for Christmas. I want to protect lives.
But he added: "Christmas is a special time of year and we've had such a hard year in 2020 - it has been such a awful year and having some hope, some joy at Christmas, I know that would be welcomed by so many people".
Businesses this week pleaded with the government to give them as much notice as possible as to what the restrictions will look like in December so they can start to plan now.
The ONS said daily coronavirus infections in England rose by an estimated 38,900 in the most recent week to November 14, down from about 50,000 the week before.More news: Google Bringing Stadia Cloud Gaming Service to iOS Through Web App