The UK needs to introduce new Covid restrictions amid rising cases and deaths, according to a scientific advisor to the Government.
Professor Andrew Hayward warned that the Government's 'Plan A', which focuses on vaccinations, would not prevent the NHS from being overwhelmed.
It comes after Health Secretary Sajid Javid denied the NHS was under 'unsustainable pressure' but admitted extra measures could return if 'behavioural changes' are not made.
NHS Confederation boss Matthew Taylor previously said measures were needed or the UK would "risk stumbling into a winter crisis".
Professor Hayward, who is a member of the Nervtag committee, told Sky News: "I think it's unlikely that Plan A is going to be sufficient to stop the NHS being overwhelmed.
"At some point we will need to move into more restrictive measures. The question of timing is really up to the politicians."
The professor said working from home would be an effective way of cutting infections.
Describing the difficulties facing the NHS, Professor Hayward said: "1,000 hospital admissions a day is a huge number.
"At any one time we've got 7,000 or 8,000 people in hospital with Covid which is equivalent of seven or eight large hospitals full of people with Covid.
"We are moving towards 1,000 deaths a week and potentially more. I think already we are already having extreme problems."
He added that waning immunity and the spike in social mixing over the past few months has fuelled rising infections.
It comes after Health Secretary Sajid Javid was asked if MPs should be setting a better example on social distancing measures.
The House of Commons benches were today packed for Prime Minister's Questions, with no Tory MP wearing a mask and Business Secretary Kwasi Kwarteng boasting about planning a Christmas party.
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One journalist asked if ministers were "telling the public to act one way and acting a different way yourselves".
Speaking at today's press conference, Sajid Javid said: "That is a very fair point. As I say, we've all got our role to play in this and we, the people standing up on this stage, we've got our public roles, as secretary of state, as someone in the NHS, as head of UKSHA, we've got big roles to play.
"But we've all got a role to play and set an example to set as private individuals as well. It's a very fair point and I'm sure a lot of people have heard you."
