London (CNN) The UK's daily death toll updates for Covid-19 could be underreporting the true number by a significant margin, according to government numbers published Tuesday.

In its daily tally of deaths, UK government counts only people who tested positive and then died of the virus in hospital. But that doesn't match the number of UK death certificates that list COVID-19 as a factor.

On Tuesday, figures released by the UK's Office of National Statistics (ONS), showed that the 1,568 people had Covid-19 listed on their death certificates between March 5, when the first death was reported, and March 27.

In contrast, death tolls released by Public Health England over the same period show only 926 confirmed deaths due to the virus in England.

There are several factors for the difference. The two tallies are counting different things -- suspected deaths versus confirmed cases that died in the hospital. There may also be a lag in reporting, as ONS have more time to record the deaths.

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