South Asian people are the most likely to die from coronavirus after being admitted to hospital in Great Britain, major analysis shows.
It is the only ethnic group to have a raised risk of death in hospital and is partly due to high levels of diabetes.
The study is hugely significant as it assessed data from four-in-10 of all hospital patients with Covid-19.
The researchers said policies such as protecting people at work and who gets a vaccine may now need to change.
Twenty-seven institutions across the UK, including universities and public health bodies, as well as 260 hospitals, were involved in the study.
The findings have been made public online ahead of being formally published in a medical journal.
However, the results were passed onto the UK government's scientific advisory group - Sage - more than a month ago.
The study tells us only what happens once somebody is admitted to hospital, not whether they were more likely to catch the virus.
It looked at nearly 35,000 Covid-19 patients in 260 hospitals across England, Scotland and Wales up until the middle of May.
"South Asians are definitely more likely to die from Covid-19 in hospital, but we don't see a strong effect in the black group," Prof Ewen Harrison, from the University of Edinburgh, told the BBC.
People from South Asian backgrounds were 20% more likely to die than white people. Other minority ethnic groups did not have a higher death rate.
The study, the largest of its type in the world, shows:
290 die out of every 1,000 white people needing hospital treatment for Covid-19
350 die out of every 1,000 South Asian people needing hospital treatment for Covid-19
The study also reveals profound differences in who is needing hospital care based on ethnicity.
"The South Asian population in hospital looks completely different to the white population," Prof Harrison said.
He added: "They're 12 years younger on average, that's a massive difference, and they tend not to have dementia, obesity or lung disease, but very high levels of diabetes."
Around 40% of South Asian patients had either type 1 or type 2 diabetes compared with 25% of white groups.
Diabetes has a dual effect of increasing the risk of infection and damaging the body's organs, which may affect the ability to survive a coronavirus infection.
Why are more people from BAME backgrounds dying from coronavirus?
This is thought to be a major factor in increasing the death rate in people of South Asian ethnicity, but the full picture has not yet been uncovered.
Other explanations could include poverty or subtle genetic differences that increase the risk of serious infection, the researchers say.