Private firms should stop offering body scans to people without any symptoms, a key government advisory panel has said.
Some clinics offer full body 'MOTS'
At the same time, anyone with symptoms seeking a private scan should be sent back to their GP, said Comare, a committee which studies radiation risk.
Unnecessary scans may increase one's cancer risk and find abnormalities that are actually benign, the panel said.
Further investigations could cause profound anxiety, and the cost of them was often footed by the NHS, it warned.
People can pay hundreds of pounds for private screening, which can involve a whole range of scans and tests to pick up potential problems.
They are designed to offer "peace of mind" to people who may not be suffering from any symptoms but who would like assurance that they have little to worry about.
The committee did not dismiss all scans outright, and stressed that targeted CT scanning of both the heart and the colon could pick up problems.
These, it suggested, could still be offered to "certain" people without symptoms.
But in addition to rejecting the full body scan, it also said there was no evidence that targeted screening of the lungs was of benefit, and that "CT should not be used for assessing spinal conditions, body fat and osteoporosis".
False positive, false negative
The recommendations come just a week after a separate report warned that private scans may do more harm than good.
"Full body MOTs" may often find benign abnormalities - so-called false positives - while missing real problems, said Professor Nicholas Wald, a specialist in preventive medicine.
Comare wants all patients to be fully informed of the likelihood of finding such false positives as well as the rates of false negative findings.
It said it had considered in particular the "subsequent psychological effects and potential physical detriment from further investigations" that were often prompted by finding such abnormalities.
But it also stressed the radiation risk, although it did concede that this was low.
An average CT scan is associated with a one in 2,000 risk of developing cancer over a lifetime, compared with one in four in the population as a whole.
But "the public health impact in terms of numbers of excess cancer cases is not negligible," the panel said.
"If 100,000 people undergo a CT scan every five years from age 40 to 70 years...then the estimated impact is approximately 240 excess fatalities."
'One for all'
John Giles, an NHS consultant radiologist and clinical director of Lifescan, said there was little in the recommendations that his firm did not comply with already.
"We offer targeted screening, and it is my firm belief that such scans save the NHS money in the long term by picking up a polyp before it develops into a cancer, for instance, and becomes much more expensive to treat.
"But what really worries me is that this report will be used by those who oppose private medicine for their own ends. The fact is: one size does not fit all, and if there are patients out there who want to take matters into their own hands, why should government stop them."
The Royal College of Physicians however welcomed the report.
"Tests that have even a minor risk should not be performed on people with no symptoms before they have received specialist advice from their consultant," said Dr Rodney Burnham.
"It is also important that scans are performed in a way that is appropriate for the condition they are intended to detect."
Sir Liam Donaldson, the Chief Medical Officer for England, said: "This report clearly points to an issue of significant concern.
"We will be consulting immediately on how best to respond to its recommendations and we will be taking the views of the public and healthcare professionals into account as part of this process."