A day after Prime Minister Boris Johnson spoke of success in dealing with the outbreak, the new figures showed the week ending April 17 was Britain's deadliest since comparable records began in 1993.

The Office for National Statistics said 21,284 people had died in England by April 17 with mentions of COVID-19 on their death certificate.

Together with figures from Scotland, Wales and Northern Ireland, the total United Kingdom death toll was at least 24,000 as of April 19.

"The United Kingdom is going to be right up there among the worst-hit nations in the initial surge," said Bill Hanage, associate professor of epidemiology at Harvard's TH Chan School of Public Health.

"With the most optimistic views of the amount of immunity that might be being generated, it would be still not be close to having enough to be able to return to normal," he told Reuters.

"The crucial part of the next stage is to have enough testing and early warning systems to avoid ending up back where the UK is now."

Unlike the hospital death tolls announced daily by the government, Tuesday's ONS figures include deaths in community settings such as care homes where overall fatalities have trebled in a few weeks.

Health Secretary Matt Hancock said on Tuesday that daily figures for deaths in the community would be published from Wednesday.

"I would push my neck out that it is plausible that there are now as many COVID-labelled deaths occurring out of hospital as there are in hospitals in England," said David Spiegelhalter, professor of the public understanding of risk at the University of Cambridge.

A UK death toll of more than 24,000 puts it among the worst-hit in Europe, exceeding France - which also counts deaths in care homes - by around 5000 at that point in time.

Britain's true toll is likely to be closer to Spain or even Italy, Europe's worst-affected countries, although their reporting of deaths outside hospital is patchy so exact comparisons are difficult.

The latest daily figures released by Britain's health ministry for COVID-19 deaths in hospitals hit 21,678 on Tuesday, a rise of 586.

Hancock said on Tuesday the coronavirus testing scheme will be opened up to a much wider pool of people including those over the age of 65 with symptoms and all care home residents.

"Anyone who is working or living in a care home will be able to get access to a test whether they have symptoms, or not," he told reporters.

In addition, he said the families of over-65s with symptoms could also get tested, as could those who are travelling to work. Previously, tests had only been available to patients, frontline staff and those in jobs designated as key workers.

Britain has more than 40 drive-through testing centres and a growing number of mobile testing centres.

Hancock also said that by the end of the week the number of home test kits available each day would rise to 25,000 from 5000.

Australian Associated Press