About 2.4 million people in the UK are waiting for cancer screening, treatment or tests, as a result of disruption to the NHS during the past 10 weeks, according to Cancer Research UK.
It estimates 2.1 million have missed out on screening, while 290,000 people with suspected symptoms have not been referred for hospital tests. More than 23,000 cancers could have gone undiagnosed during lockdown.
Chief executive Michelle Mitchell said COVID-19 has placed an "enormous strain on cancer services". "The NHS has had to make very hard decisions to balance risk," she said.