On Tuesday, NHS England has announced 778 new deaths of people who tested positive for coronavirus.
The total number of confirmed reported deaths in hospitals in England has risen to 15,607.
England and Wales announced a further 873 deaths bringing the UKs total to 17,382.
A report by the Office for National Statistics (ONS) suggests the true number of deaths is around 40% higher, with a third of all people who died in April had coronavirus.
By 10 April the ONS recorded 13,121 deaths across the UK. Data in Wales and England show 1,644 died in care homes by 10 April.
The Department of Health figures had, by 10 April, announced only 9,288 fatalities, but the backdated deaths increased by a total by 41.2%.
This suggests the death toll of 16,509 confirmed on Monday, could be much closer to 23,000 deaths across the UK.
Statistician for the ONS, Sarah Caul, said, “The figures published on GOV.UK are valuable because they are available very quickly, and give an indication of what is happening day by day.
“But they won’t necessarily include all deaths involving COVID-19, such as those not in a hospital.”
As countries are easing lockdown measures the WHO are warning of a second wave which could be more deadly than what the world has seen thus far.
He told reporters at a press briefing at the WHO headquarters in Geneva, “Trust us. The worst is yet ahead of us.