The new shadow social care minister has called on the government to include fatalities from Covid-19 outside hospitals in its daily death toll, after the Guardian revealed that hundreds of people had died from the virus in care homes and not yet been counted.

In a letter to the health secretary, Matt Hancock, Liz Kendall, who ran for the Labour leadership in 2015, said she had serious concerns that deaths of people in care homes were not being reported “in a timely manner”.

The Guardian reported on Thursday that the industry body Care England estimated that the coronavirus death toll in care homes was likely to be close to 1,000, despite the only available official figure being dramatically lower.

Unlike hospital deaths, statistics for coronavirus fatalities in the community are only released weekly. The Office for National Statistics published figures for deaths in care homes for the first time on Tuesday, saying 20 people had died across the whole of England and Wales in the week to 27 March.

That figure is 12 days behind the daily hospital death rate and relies on registered death certificates, which take an average of five days to process. With a time lag of around 17 days, social care operators say the scale of infection and fatalities is not being grasped.

“This delay obscures the scale of the spread of Covid-19 in care homes and the impact on some of the most vulnerable people in our society,” wrote Kendall, who was appointed shadow minister for social care by the new Labour leader, Keir Starmer.

“I therefore urge you to put in place a system where deaths relating to Covid-19 outside of hospital, including in care homes, are collected and reported regularly to the Department of Health and Social Care and published daily alongside deaths in hospitals.

“For families and care staff, accurate and timely reporting of deaths of people in care homes is an essential step in tackling this problem and saving as many lives as possible. It will also enable the government to focus its efforts on ensuring all care staff get the PPE and testing they need.”

Despite the low official figure, more than 120 residents of the UK’s largest charitable provider of care homes are thought to have died from the virus in the last three weeks, while another network of care homes is reported to have recorded 88 deaths.

Care industry leaders and the Alzheimer’s Society told the Guardian that they believed the virus to be active in around half of care settings, which look after about 400,000 people in the UK. However, Prof Chris Whitty, the UK government’s chief medical officer, said on Tuesday that just over 9% of care homes had cases of Covid-19.