Coronavirus-related deaths were 41% higher in England and Wales than the government's official figures in the week to 10 April.
The new figures, revealed in an Office for National Statistics report, take into account deaths outside of hospitals.
They show that there were more than 1,000 COVID-19-related care home deaths registered up to April 10, up from 217 the week before.
Labour's shadow social care minister Liz Kendall said the figures demonstrate the "terrible toll" that the virus is having on elderly and disabled people in care homes.
"Yet these awful figures are only scratching the surface of the emerging crisis in social care, because they are already 11 days out of date," she said.
"The government must now publish daily figures of Covid-19 deaths outside hospital, including in care homes, so we know the true scale of the problem.
"This is essential to tackling the spread of the virus, ensuing social care has the resources it needs and getting vital PPE and testing to care workers on the frontline."
Source: Sky News