Professor Linda Cardozo, of King's College Hospital, London, says little evidence exists to advise women on the safety or effectiveness of procedures.
These include operations to make the external appearance more "attractive" and reshaping the vagina to counter laxity after childbirth, for example.
She discussed the issues at a medical meeting in Montreal, Canada.
Women want to emulate the supermodel. It's part of a trend
A Google search showed over 45,000 references to cosmetic vaginal surgery, yet on medical databases such as PubMed or Medline there were fewer than 100.
Professor Cardozo said the most established vaginal cosmetic procedure was reduction labioplasty - a procedure to make the labia smaller - which is requested by women either for aesthetic reasons or to alleviate physical discomfort.
"Women want to emulate the supermodel. It's part of a trend. But they should know that all surgery can be risky.
"Most of the procedures are done in the private sector and it's totally unregulated."
The exact numbers of procedures carried out are unknown.
In the past five years there has been a doubling of the number of labial reductions carried out on the NHS from 400 in 2000/1 to 800 in 2004/5.
The evidence from existing case studies shows that the procedure, which costs about £2,000 at a private clinic, does have positive aesthetic results but it is unclear whether it resolves feelings of psychological distress or improves sexual functioning, she said.
And there was little evidence that "vaginal rejuvenation" - the surgical repair of vaginal laxity, with a price tag of about £3,000 - improved symptoms and was any better than doing simple pelvic floor muscle exercises.
She said robust research was needed so that doctors could properly advise their patients. In the meantime, she urged surgeons to remain cautious and operate only as a last resort.
In her presentation at the Royal College of Obstetricians and Gynaecologists 7th International Scientific Meeting, Professor Cardozo said: "Cosmetic vaginal procedures raise a number of serious ethical questions.
"Women are paying large sums of money for this type of surgery which may improve the appearance of their genitalia but there is no evidence that it improves function."Found this Post interesting? Discover more Curious Reads.