Britain reported 3,383 new Covid cases on Monday, figures show - the sixth day in a row daily infections have topped 3,000.
One death was recorded, according to Government data.
The rise in cases comes amid growing fears the lifting of lockdown on June 21 will be delayed.
Scientists have warned that a third wave could already be underway in Britain as the Indian variant spreads.
Daily infections crept above 3,000 for the first time since April 12 on May 26, when 3,180 were reported.
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They have not dropped below 3,000 since, with 4,182 recorded on May 28.
The data from May 31 comes as pictures emerge of Brits flocking to the beach and parks on Bank Holiday Monday - the hottest day of the year so far.
Numbers also tend to be lower after a weekend due to a lag in reporting.
The latest figures have also been released in the wake of an expert claiming vaccines are offering a "false sense of security" amid a mounting third wave of infections.
Professor Ravi Gupta, a member of the New and Emerging Respiratory Virus Threats Advisory Group (Nervtag), said that with Britain in the grip of an "early" third wave of Covid-19 infections, 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, but that the "explosive" impact it could have was currently being masked by the high vaccination rate.
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.
When asked about the possibility of a delay to freedom from restrictions, Environment Secretary George Eustice said nothing could be ruled out.
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.
Prof Gupta told BBC Radio 4's Today programme: "It will probably take longer than earlier waves to emerge because of the fact that we do have quite high levels of vaccination in the population, so there may be a false sense of security for some time, and that's our concern.
"I think the problem is we are not too far from reaching the sort of levels of vaccination that would help us contain the virus and I think that people are not saying we should abandon the June 21 date altogether but just to delay it by a few weeks while we gather more intelligence and we can look at the trajectory in a clearer way.
"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 added that 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.
