The number of patients admitted for routine treatment in hospitals in England was down 67% in June compared with the same time last year, NHS figures show.
The number of people going to accident and emergency units in England in July was also down on last year, by 30%.
The coronavirus pandemic has caused disruption to many areas of the health service.
But patients are being urged to seek help from the NHS when they need it.
NHS England said local staff were working hard to restore non-Covid services and record numbers had received help during the pandemic through NHS 111.
‘Alarming backlog’
Meanwhile, the number of people going to their GP with symptoms of cancer and being urgently referred to a specialist is rising but still nearly 20% lower than the same time last year.
A total of 153,134 urgent cancer referrals were made by GPs in England in June, compared with 194,047 in the same month last year.
NHS England said more than 92% of people were having their cancer symptoms investigated within two weeks and 85,000 people had started treatment for cancer since the pandemic began.
But Macmillan Cancer Support said the figures were “still worryingly low”.
Head of policy Sara Bainbridge said: “These results from June suggest an alarming backlog of undiagnosed cancer and a growing number of people who are yet to start treatment.
“This could directly impact on many of these people’s chances of survival.”