Hundreds of girls aged 14 and younger have had 'designer vagina' surgery, according to new figures.
Researchers said 343 operations – which involves reshaping genitalia - were carried out on the NHS over last six years.
The statistics aren't broken down further, but it is thought the operations would have been carried out for cosmetic reasons and on the grounds that the 'problem' is psychologically damaging.
Some experts fear the demand is driven by the pornography industry and explicit reality TV shows where all performers have perfectly symmetrical body parts.
Dr Sarah Creighton, who led researchers from University College Hospital, London, told BMJ Open: "In the past six years, 343 labiaplasties were performed in the UK NHS on girls aged 14 or under.
"The indications for surgery in this group of children are unknown, but labial anomalies requiring surgical interventions are extremely rare.
"In a recent observational study of referral patterns, girls as young as nine years with normal labia had presented for labiaplasty.
"The labia minora change as part of normal pubertal growth, with development completed as the individual approaches adulthood.
"Given the fact that anatomy continues to change throughout the lifespan, the younger a girl begins her FGCS journey the higher the number of lifetime operations and the greater and more multiple the risks.
"The NHS collects information about the number of these procedures and the age range but there is no requirement to record the reasons for them.
"We do not know what they have been done for, we can only speculate and more information is needed."
The researchers say demand may be growing for such procedures because of poor and inaccurate information available on the internet, usually from private clinics.
However, a Department of Health spokeswoman said: "There is no such thing as a designer vagina on the NHS.
"Of course there is cosmetic surgery carried out on the NHS, but this is only for patients who have a clinical need for it - absolutely not for those who would simply like to have it done."