Coronavirus deaths in care homes in England could be more than twice as high as the number already reported, the government has said.
The Department of Health has said it also feared a “significant rise” in deaths not related to coronavirus among residents.
It comes as the death toll in UK hospitals rose by 763 to 18,100.
And Health Secretary Matt Hancock announced that 15 social care workers had died in the pandemic.
He told MPs: “In the same way that we pay tribute to and we remember all of those NHS staff who have died, so too we do for those who serve our country and look after people in social care.”
The daily death figures from UK hospitals have been one of the main statistics used by the government to track the progress of the pandemic.
The government has always been clear that it does not include people who die in care homes or in their own homes.
The reporting mechanism for such deaths is different from that used by hospitals and the data can take longer to pull together, because there are far more care homes than hospitals.
On Tuesday, figures published by the Office for National Statistics suggested there had been 975 coronavirus deaths in care homes in England by 10 April.
But on Wednesday, the Care Quality Commission (CQC) – the NHS and care regulator – and the government issued a statement saying the number of deaths in the five days following 10 April, could be double that.
“It is anticipated that the number of deaths in care homes relating to Covid-19 reported by providers between 11 April and 15 April could be double the number of care home deaths reported yesterday (Tuesday).
“In common with the ONS, CQC’s preliminary analysis also indicates there may be a significant rise in non-Covid-19 deaths.”
The final figures will be published on 28 April, once verified.
Care homes in England have always had to notify the CQC when a resident dies.
But the forms have now been adjusted to collect information on whether a death is linked to coronavirus.
Matt Hancock said: “All deaths in care homes are, of course, recorded.”
But he warned against comparing the different figures to make conclusions about the overall death toll, saying they were compiled on different time frames and needed “rigorous analysis” to ensure the comparison was accurate.
Doubling in five days sounds terrifying, but that is the story of the epidemic.
The number of deaths announced for the UK as a whole was doubling every three days up to the week before Easter.
After that, it slowed down to doubling every week before growth eventually stalled.
So this trend for care homes from a week ago is not very different to ones we have seen elsewhere.
Their new data is preliminary and we should be careful about comparing the first week of their data to ONS figures from the preceding week.
But the big issue has been about knowing what’s happening in care homes now: has growth in deaths stalled there too or are they continuing to climb?
The other data sources we use don’t have the answer. Those daily figures from DHSC mainly cover deaths in hospitals, so miss most care home deaths.
The complete figures based on death certificates that capture care homes take over a week to be collated and analysed.
The Care Quality Commission are notified of every death of a care home resident, so can give a fuller picture.
But when they are included in official figures, it will give us critical information about a group of people who are among the most vulnerable to the coronavirus.
It comes as the government faces increasing pressure to address a shortage of personal protective equipment (PPE) for care home workers, amid reports of staff, or their employers, having to pay inflated prices for masks and gowns.
Labour former cabinet minister Lord Hain said: “The government needs urgently to give billions more to care homes instead of leaving them so badly in the lurch during this crisis.”
Acting Liberal Democrat leader Sir Ed Davey told the BBC the CQC figures were “alarming” and accused the government of being “very slow in responding”.
“We are now seeing what appears to be a huge number of deaths,” he added, and he called on the government to “get it’s act together”.