The number of people killed by the coronavirus in Britain's care homes could be as high as 7,500, the sector's main charity warned.
The comments came as the country's overall official toll soared by 888 on Saturday to 15,464.
Care England, Britain's largest representative body for care homes, said that estimates based on some of the death rates since April 1 suggested up to 7,500 people may have died of the virus.
"Without testing, it is very difficult to give an absolute figure," Martin Green, chief executive of Care England, told The Daily Telegraph.
"However, if we look at some of the death rates since April 1 and compare them with previous years' rates, we estimate a figure of about 7,500 people may have died as a result of COVID-19."
The figure is more than five times higher than the estimate of 1,400 suggested by the government earlier this week.
It is also far in excess of the 217 care home deaths recorded by the Office for National Statistics (ONS) up to April 3, the most recent date for which official data is available.
Britain's official coronavirus toll only includes deaths recorded in hospitals, which can take some days to register fatalities.
The ONS said this week that its data suggested that deaths in hospital accounted for around 85 percent of all coronavirus fatalities in the country.
This figure was calculated by comparing overall excess deaths in the country to the official coronavirus toll.
But the Care England estimate would mean that deaths in hospital account for a far lower proportion of the true total than the ONS data suggested.
"This is a shocking and utterly heartbreaking estimate that will send a chill down the spine of anyone with a loved one living in a care home," said Caroline Abrahams, charity director at the Age UK charity.
"As we have feared for some time, what's going on in care homes –- not only here but in many other countries too –- is a tragedy in the making."
Care England did not publish the data underlying its estimate, but Health Secretary Matt Hancock told parliament's health and social care committee on Friday that figures would be published "very shortly".
Care home bosses have accused the government of a "shambolic" response to the sector's crisis, particularly over "haphazard" deliveries of personal protective equipment (PPE).
Around 94 percent of care home beds in Britain are in private hands, with "a large number of them owned by international private companies," according to The Centre for Health and the Public Interest thinktank.
Concern over PPE is not restricted to care homes, with frontline staff in some of Britain's state-run hospitals warning they could run out this weekend.
Chris Hopson, chairman of NHS Providers, said we have "reached the point where national stock of fully fluid repellent gowns and coveralls (is) exhausted".
A leaked Public Health England document revealed health workers are being asked to reuse protective gowns and masks as a "last resort".
The government announced this week that the country would be locked down for at least three more weeks, while Buckingham Palace said on Saturday that Queen Elizabeth II will not celebrate her 94th birthday on Tuesday with a traditional gun salute due.
"There will be no gun salutes. Her Majesty was keen that no special measures were put in place to allow gun salutes as she did not feel it appropriate in the current circumstances," a palace official told AFP.