Melanoma is a particularly aggressive form of cancer
There needs to be greater regulation and tougher standards for privately-run high street mole clinics, a leading medical journal says.
The Drug and Therapeutics Bulletin said rising concern about skin cancers meant the public were increasingly turning to high street clinics to get check-ups.
But it warned the services were not properly regulated and were often staffed by ill-qualified nurses.
Dermatologists urged people who had skin concerns to see their GP.
The rising usage of mole clinics was highlighted in a report by the All Party Parliamentary Group on Skin last year.
It said demand for mole-scanning services had risen in line with the rise seen in cancers.
Over the past four years cases of mole-related malignant melanomas have risen by nearly a third in men and a fifth in women and now claim 2,300 lives a year.
It is not known exactly how many people are using the private clinics.
But the Drugs and Therapeutics Bulletin, part of the British Medical Journal family of publications, suggested patients could be at risk from the services being offered.
The journal said some were staffed by nurses with only one or two weeks' training in the diagnosis of skin lesions.
Editor Dr Ike Iheanacho said: "The problem is that there are just not enough dermatologists to meet demand.
"GPs often don't have the knowledge and experience to deal with the cases so people turn to private clinics, but the standards are just not there."
Mole clinics fall into a grey area in terms of regulation.
NHS centres and private providers offering surgery are all overseen by the Healthcare Commission, but those private clinics offering more basic services, such as scans, do not necessarily need to be registered with the watchdog.
Dr Iheanacho said they should be forced to adhere to NHS standards and guidance and come fully under the remit of regulators.
A spokeswoman for the British Association of Dermatologists said they had concerns about the trend, pointing out many private clinics end up referring patients back to the NHS.
She added: "Patients concerned about a mole should seek advice from their GP and ask for referral to a dermatologist if there is concern, all of which can be done free on the NHS."