Two of the UK's largest care home providers have announced the death of 521 residents in recent weeks.
The figures come in the wake of calls for the government to announce the full scale of deaths outside of the NHS.
HC One which operates over 300 care homes across the UK announced 311 deaths up to 8pm on April 13.
MHA, based in Derby, announced 210 deaths across 131 of its homes.
ONS figures also revealed
The worrying figures were released concurrently with ONS figures which revealed that 406 deaths involving Covid-19 had been recorded in England and Wales up to April 3 outside of hospitals.
The figures are released on a weekly basis with a ten-day time lag.
Of the 406 deaths, 217 took place in c are homes, 136 in homes, 33 in hospices, 3 in communal establishments and 17 elsewhere.
The equivalent figure for hospital deaths over the time is 3,716.
In London, almost half (46.6%) of deaths registered in the week ending April 3 involved Covid-19, while the virus accounted for 22.1% of deaths registered in the West Midlands.
15% higher than NHS numbers
Nick Stripe, head of health analysis and life events at the ONS, said: "The latest comparable data for deaths involving Covid-19 with a date of death up to 3 April show there were 6,235 deaths in England and Wales.
"When looking at data for England, this is 15% higher than the NHS numbers as they include all mentions of Covid-19 on the death certificate, including suspected Covid-19, as well as deaths in the community.
"The 16,387 deaths that were registered in England and Wales during the week ending 3 April is the highest weekly total since we started compiling weekly deaths data in 2005."