Female cosmetic genital surgery – so-called “designer vagina” operations – are almost always unnecessary, can be harmful, and should not be offered to girls under the age of 18, leading experts have said.

More and more women, including adolescents, are seeking the procedures because of a “distorted” image of what is normal presented in popular culture, pornography, and private clinic’s own advertisements, the Royal College of Obstetricians and Gynaecologists (RCOG) Ethics Committee said.

The number of labial reductions – the most common procedure – carried out by the NHS has increased five-fold in the past decade, with 2,000 performed in 2010. But this could be just “the tip of the iceberg” because private clinics do not have to record data, according to joint reports from RCOG and the British Society for Paediatric and Adolescent Gynaecology (BritSPAG).

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Experts said the procedures should not be offered to under-18s except in extremely rare circumstances where it was medically necessary, and should not be offered to anyone on the NHS without a clear medical justification.

Clinicians also need to do more to inform women about natural variations in genital appearance, said Dame Suzi Leather, chair of the RCOG Ethics Committee.

“Providing patients with a much more accurate range of what is normal will help them make more informed choices,” said. “If you are anxious about your genitals and you look things up on the internet you either come across advertisements for cosmetic surgery or you come across pornography. You don’t come across information on what normal, healthy vulvas can look like.”

There was also a lack of reliable evidence that such procedures have a positive outcome for women who report feeling discomfort when wearing tight clothes or during sex, experts said.

NHS figures do not show the reasons women sought out cosmetic genital surgery, nor what the outcome was. However, BritSPAG said there had been no increase in “incidence of labial pathology” that could account for the increased number of operations.

Dame Suzi said she was particularly concerned that girls under 18 were being offered the procedures, as the risks of complications are higher if surgery is performed before full genital development has been completed.

Between 2008 and 2012, 266 labial reductions were performed on girls under 14 in the NHS, according to official statistics.

Paul Banwell, a consultant plastic surgeon and member of the British Association of Aesthetic Plastic Surgeons, said that the number of under 18s offered labiaplasty at his clinics was “very small” and said all patients were told their anatomy was normal. However, the operation could have “quality of life benefits”, he added.

“We have to be sensitive of the fact that, just as some ladies have large breasts and want smaller breasts, exactly the same thing can happen with the labia. There is a role for the operation and patients will benefit,” he said.