The UK announced another 33,470 positive coronavirus cases on Thursday – 39 per cent more than the same time last week. The figure was the highest in the country since the coronavirus outbreak hit and comes a week after the second lockdown began.
Scientists believe the sudden spike could have been caused by people rushing to socialise before the strict measures came into force.
Professor Carl Heneghan, director of the Centre of Evidence-Based Medicine at Oxford, said: “These figures are going through the roof, and it's not really surprising when we saw scenes like Christmas Eve last week before we went into lockdown.
Speaking to the Telegraph, Prof Heneghan added: “The problem is when these policies are drawn up the Government assumes everyone will behave the same way, and they just don't take account of the fact that many people saw it as a last chance to get out.'
Paul Hunter, medicine professor at the University of East Anglia, also said socialising ahead of lockdown may have been a factor in the record spike. He told the same newspaper: “If cases remain this high for another day or so then it will pretty much be down to people having more social contacts – partying before lockdown.”
Dr Yvonne Doyle, medical director at Public Health England, said the highest rates of infections were among younger generations. But she said: "Worryingly it is rising quickly in those over 80 who are most at risk of poor outcomes.
"The current measures are in place to help protect all of us, and anyone can suffer serious illness from this virus.
"The majority of cases reported today were from tests carried out on the 9th and 10th of November, which includes infections acquired in the days leading up to new measures on the 5th November.
"Limiting contact with others will help to stop the spread of the virus and protect the people we love."
However, Professor Stephen Powis, NHS England's medical director, played down the increase at a Downing Street press conference on Thursday evening.
He said: "It is important to look at the number of cases reported over a number of days and not just take one day in isolation. It is clear that infection rates have been going up. What is really important is to get those infection rates down."
He said it was "too early to say" whether England's national lockdown was having an effect, but warned people not to expect life to return to normal when restrictions are lifted on December 2. "We will not be going back completely to normal - there will need to be other measures in place because while this virus is still here, we need to ensure that infection rates stay as low as possible and that we reduce the chance of transmission."
Separately, research by Imperial College London's React study suggested around 100,000 new coronavirus infections were occurring per day in England at the start of the second lockdown last week.
Experts said infections rose sharply across the country with more than one in 80 people infected, double that reported in early October. They observed a drop in prevalence at the end of last month but then a quick uptick at the start of November.