Professor Ravi Gupta, a member of the New and Emerging Respiratory Virus Threats Advisory Group (Nervtag), said ministers should consider pushing back their target of scrapping all Covid measures on June 21 “by a few weeks”.
The University of Cambridge academic said there had been an “exponential growth” in the number of cases, fuelled by the more transmissible Indian variant.
It comes as NHS chiefs warned that the lockdown-induced backlog of treatments for ailments other than Covid mean that even a small increase in the number of coronavirus patients could cause hospitals to be overstretched once again.
With both deaths and cases up significantly in the past week, experts are urging the Prime Minister to keep to his “data not dates” approach to easing lockdown.
Between May 24 and 30 there were 60 deaths reported within 28 days of a positive coronavirus test, an increase of 42.9 per cent compared with the previous seven days.
Sunday also saw a further 3,240 lab-confirmed cases in the UK, with the number of cases between May 24 and May 30 – 22,474 – 26.8 per cent higher than the previous seven days.
Prof Gupta told BBC Radio 4’s Today programme: “If you look at the costs and benefits of getting it wrong, I think it is heavily in favour of delay.”
Cabinet minister Mr Eustice said the Government wanted to monitor the data before making a final decision on whether to go ahead with its June 21 plans to abolish social distancing and limits on socialising.
Pressed on whether businesses should prepare for a delay to the unlocking, Mr Eustice replied: “I’ve said all along, as has Matt Hancock and the Prime Minister, we can’t rule anything out because we know this has been a difficult pandemic, a dynamic situation.
“We have to make that judgment a couple of weeks before.”
Chief executive of NHS Providers Chris Hopson said even a small uptick in severe cases was likely to hit the health service as it recovers from the winter-into-spring lockdown.
He told Times Radio: “The concerns are that this is a much more transmissible variant. We’ve still got lots of people still to vaccinate. And absolutely hospitals are very busy.
“We’re talking to people who are saying ‘We’ve got 96-97 per cent bed occupancy, this is not the kind of bed occupancy we would normally expect at this time of year’.
“We’re trying to go full pelt, to recover those care backlogs, we seem to be getting more people coming in on the urgent and emergency care pathway than we were expecting.”