This is higher than previously thought, as health service data released last week suggested that 26% of Covid-19 victims in English hospitals had the disease.
The new figures show that, in total, 7,466 coronavirus patients who died in hospitals in England had type 2 diabetes.
Another 365 who died had type 1 diabetes.
This represents approximately 32% of the 24,739 deaths from Covid-19 recorded in English hospitals as of May 17.
The figures released on May 14 suggested that 5,873 diabetes patients died with Covid-19 out of 22,332 at the time.
The study's lead author, Professor Jonathan Valabhji, called the finding "worrying news" and said it "shows the extent of coronavirus risk for people with diabetes".
He added: "Importantly, it also shows that higher blood glucose levels and obesity further increase the risk in both types of diabetes."
Charity Diabetes UK is asking the government to ensure that patients are kept safe at work and can access other support systems, such as supermarket delivery ranges and emotional support.
The organization's policy director, Bridget Turner, said: "We know that people with diabetes will want to know what they can do to stay safe.
"The most important thing that anyone with diabetes can do is try their best to control their condition carefully, keeping blood sugar as high as possible."
"All people with diabetes must also follow strict social distance measures to reduce their chances of getting the virus completely."
According to data released last week, there were more deaths recorded from patients with diabetes than those with other comorbidities.
About 4,048 (18%) of those who died in hospitals in England since March 31 had dementia and 3,254 (15%) reported having chronic lung disease, while 1,549 patients had asthma.
NHS England is offering video consultations and online consultations, as well as routine discussions with general practitioners, so that diabetes treatment can continue throughout the pandemic.
They also created a dedicated helpline with Diabetes UK to help people who use insulin.