After months of low numbers of new cases and deaths, a new real-time study showed higher prevalence of the coronavirus across the UK, with Prime Minister Boris Johnson describing the situation as a “critical moment”.

As of Wednesday evening, 7,108 new cases were reported across the UK – more than the daily peaks in April and May, prompting renewed concern and more restrictions in several areas, particularly in north England.

Facing criticism from Labour over the government’s handling of the pandemic, Johnson implored people to follow guidelines, as they did earlier this year, when the virus was suppressed for months, before resurging in September.

Another national lockdown remains an option, he declared.

As government’s top experts cautioned about “things going in the wrong direction”, Johnson said: “(No) matter how impatient we may be, how fed up we may become, there is only one way of doing this, and that’s by showing a collective forbearance, common sense and willingness to make sacrifices for the safety of others”.

“At this critical moment, when I know people will be wanting to know the details, I will be providing regular updates through these press conferences. And I have to be clear, that if the evidence requires it, we will not hesitate to take further measures that would, I’m afraid, be more costly than the ones we have put into effect now”.

Johnson adopted a markedly different approach from that of chancellor Rishi Sunak, who last week exhorted Britons to “learn to live with it (coronavirus) and live without fear”, while outlining new measures to protect millions of jobs affected by the pandemic.

Johnson said: “I know some people will think we should give up and let the virus take its course, despite the huge loss of life that would potentially entail. I have to say, I profoundly disagree”.

“And I don’t think it’s what the British people want, I don’t think they want to throw in the sponge, they want to fight and defeat this virus and that is what we are going to do,” he added.

Researchers at Imperial College London said an interim report from the largest testing programme has found high infection prevalence across the UK and that cases have continued to rise, based on results from swab tests carried out by more than 80,000 people out of a total of 150,000, taken between September 18 and 26.

The biggest rise in cases was found in those aged over 65, which saw seven times as many cases as previously. A similar increase was found in those aged between 55-64. Young people continued to have the highest rates of infection, with 1 in 100 estimated to have the virus.

The reproduction (R) number decreased from 1.7 to 1.1 but with a wide possible range for the recent value of 0.7 to 1.5. This suggests that the rate of new infections has decreased, but an R above 1 would mean cases will continue to rise if current trends continue.

Paul Elliott, director of the Real-time Assessment of Community Transmission (REACT 1) at the college, said: “While our latest findings show some early evidence that the growth of new cases may have slowed, suggesting efforts to control the infection are working, the prevalence of infection is the highest that we have recorded to date”.

“This reinforces the need for protective measures to limit the spread of the disease and the public’s adherence to these, which will be vital to minimise further significant illness and loss of life from Covid-19.”