Private medical screening needs to be subject to stricter regulation, government advisers believe.
The National Screening Committee is currently considering how to regulate the industry amid fears that the sector does not undergo proper checks, Pulse magazine reports.
Programme director Sir Muir Gray told Pulse that private testing is "an example of low-value activity which generates work for the health service, may cause harm and does not benefit the individual".
He suggested that some private clinics perform tests on patients and then simply send them to their GP for further tests on the NHS.
Health screening has been accused of causing unnecessary anxiety for patients, but Dr Peter Mace, assistant medical director of Bupa Wellness, denied the claim.
"We refute the allegation that health assessments cause patients anxiety. Our experience is quite the opposite," he told BBC News.
"We identify a health issue for around a third of customers which they were previously unaware of," he added.
Independent advice on private healthcare