Watch: Christmas is the best time for new lockdown measures, says Oxford expert
Carl Heneghan told Sky News' Sophy Ridge that it was time for a "calm and cool" approach to the increase in coronavirus cases.
He said it mirrored the "seasonal effect" of other respiratory infections, such as the common cold, which increase significantly at the end of the year.
"What we have to do now is slow down," said Prof Heneghan. "This is a long winter. We cannot afford to go now with harsh measures... The impact on the economy is going to be significant because what happens is as soon as you pause, then you open up again, it tends to come back."
The prime minister is said to be reluctantly weighing up new national lockdown rules similar to those introduced in large parts of England, such as curfews in restaurants and pubs and stopping households mixing.
Health Secretary Matt Hancock told Sky News on Sunday that the UK faced a "tipping point" where "more restrictive measures" could be brought in. But Prof Heneghan - a vocal critic of the government's approach who leads Oxford's Centre for Evidence Based Medicine - said any intervention would be more useful over the festive period.
"I'd be looking at the Christmas break right now - to extend it," he said. "Often when we come back in January, there's a significant rise in deaths - about 5,000 per week more than what we see right now. And that's due to the seasonal effect.
"Therefore, if you're looking at a break and when we need it, you're looking at the mid-winter when we might run into problems.
"It would be more explainable to people why we're doing it then than now."
It comes as the testing system struggles with demand and as daily infection figures rose to a 4,422 reported on Saturday - the highest since 8 May.
However, that is still far smaller than the peak of the outbreak when testing was also not widely available in the community.
Prof Heneghan told Sky News there was no evidence of a second wave and accused the government of considering a narrow range of views. He said "too many non-clinical people [are] focussing on a single disease" and that professionals on the frontline were not getting chance to have proper input.
"Slow down - get a wider range of expertise in the room so you can make a much more balanced decision about what you're going to actually do and its impact - not just on COVID - what about all the other infections? What about all the cancers, heart disease?"
A "control plan" to shield people in care homes and simpler messaging on the virus is also needed, said Prof Heneghan. "What you're seeing among the population is a single message that is now missing: that if you have symptoms you have to isolate. "And I'm picking up a lot of people who just do not understand that because we haven't been clear about that messaging."
Health Secretary Matt Hancock told Sky News that people must become stricter on following coronavirus rules and guidance, saying they had "got more relaxed over the summer".
He said he was "worried" too many were breaching self-isolation guidance, leading to new fines coming in of up to £10,000 for rule-breakers. Any new national lockdown rules could be challenged in parliament however.
Sir Graham Brady, chairman of the powerful Tory backbench 1922 Committee, wants to force the government to put any new measures to a vote of MPs.
He told The Sunday Telegraph he would take action when the government comes to renew the emergency powers in the Coronavirus Act 2020.
"There is now no justification for ministers ruling by emergency powers without reference to normal democratic processes," he told the newspaper.