The UK recording the highest single-day figure of coronavirus cases since the outbreak began has been described as a “stark warning” by a top public health official.

As of 9am on Thursday, there had been a further 6,634 lab-confirmed cases of Covid-19 across the four nations, taking the overall number of cases confirmed to 416,363.

Experts have previously warned that describing the daily figure as a record could be “misleading” as it is not clear how many people were actually infected during the height of the first wave due to a lack of community testing at the time.

Testing capacity has greatly increased since then.

But Professor Yvonne Doyle, medical director at Public Health England, said the rise in new cases provides a “clear” signal and insisted people must follow the stricter measures announced this week in order to help control the virus.

She said: “This is the highest number recorded and a stark warning for us all. The signals are clear.

“Positivity rates are rising across all age groups and we’re continuing to see spikes in rates of admission to hospital and critical care.

“We must all follow the new measures that have been brought in to help control the virus and download the new NHS Covid-19 App which is the fastest way of knowing when you’re at risk.”

The app launched in England and Wales on Thursday.

Scotland and Northern Ireland have their own apps, called Protect Scotland and StopCOVID NI respectively.

The Government also said a further 40 people had died within 28 days of testing positive for Covid-19 as of Thursday, bringing the UK’s total deaths to 41,902.

Separate figures published by the UK’s statistics agencies show there have now been 57,600 deaths registered in the UK where Covid-19 was mentioned on the death certificate.

Professor James Naismith, director of the Rosalind Franklin Institute, said while science and medicine will help to lower the expected rise in deaths, the public must also play its part.

He said: “The rise in cases is yet further confirmation that the virus is spreading rapidly. This will result in increased pressure on hospitals, more serious illness and a rise in deaths which will bring tragedy.

“Scientific and medical advances will lower the toll.  We all need to do our part.”

He added that while the latest daily cases figure is large, it is “only a fraction” of the cases in the early part of the pandemic.

“The fact that we will soon set a record of daily cases is because we did not measure in March,” he said.

Speaking to Sky News on Thursday, Health Secretary Matt Hancock said almost 10,000 people a day are contracting coronavirus, fewer than the 100,000 per day estimated during the spring peak.