Medical experts have sounded the alarm over soaring rates of labiaplasty, as the preliminary findings of a study show women are increasingly turning to private providers to pursue "designer vaginas".

NHS and private sector professionals have warned that some young women approaching cosmetic surgery companies are depressed or on medication, and are being sold operations without preliminary access to alternative psychological therapies.

Experts carrying out the research at King's College London also suggest that the so-called "pornification" of modern culture may be driving up surgery rates to unprecedented levels as both men and women have increased exposure to pornographic imagery via the internet. Recent studies have shown sharp rises in the numbers of young people accessing porn.

The King's study is attempting to find out more about the motivations of women who are increasingly seeking surgery. Professor Linda Cardozo, a gynaecologist, said that the preliminary findings show that while women go to the NHS seeking help with functional problems, such as discomfort during sex, those turning to private companies were often seeking purely cosmetic changes and were placing themselves at risk in a growing industry that is largely unregulated. Experts say the risks of labiaplasty include permanent scarring, infections, bleeding and irritation, as well as increased or decreased sensitivity if nerves get caught in the operation.

"The private sector is not recorded, audited or regulated," said Cardozo. "We have no way of knowing how many surgeries take place there. It's possible to go on a [surgery] course for $75,000 in the US, come back with your own laser equipment and set up. At least if you have it on the NHS you have to go through your GP and that's a gatekeeper."

Cardozo also expressed concerns that private providers could be acting irresponsibly by operating on vulnerable women in need of psychological care.

Cosmetic surgeon Angelica Kavouni is carrying out three labiaplasties a week, both for the NHS and for her private company, Cosmetic Solutions, where she charges £3,000 per operation. She said: "A lot who come to me for labiaplasty are depressed and some are on medication. That's a major issue, because you shouldn't have cosmetic surgery when you are like that. It definitely needs to be investigated."

The number of labiaplasty operations in Britain is booming. The surgery is primarily intended to make labia smaller or more symmetrical. Figures released to the Observer show that the Harley Medical Group, a leading cosmetic surgery provider across the UK, received more than 5,000 enquiries for cosmetic gynaecology in 2010, 65% of which were for labial reduction, the rest for tightening and reshaping.

Similar increases have also been experienced by the NHS. A study published in the British Journal of Obstetrics and Gynaecology in 2009 revealed that there had been an almost 70% increase in the number of women having labiaplasty on the NHS on the previous year. There were 1,118 operations in 2008, compared with 669 in 2007 and 404 in 2006.

A partner in the King's University research, Dr David Veale, a consultant psychiatrist in cognitive behaviour therapy, said he believed the surge in demand could be linked to easier access to explicit sexual imagery. "We haven't completed the research, but there is suspicion that this is related to much greater access to porn, so it is easier for women to compare themselves to actresses who may have had it done. This is to do with the increasing sexualisation of society – it's the last part of the body to be changed."

Dr Veale also expressed concerns that some women seeking surgery, the majority of whom seem to be under 30, were receiving labiaplasty on the mistaken impression that it might solve psychological problems such as body dysmorphic disorder, a condition that causes sufferers to obsess with a part of their body.

"Most people go straight to cosmetic surgery and say they've got a problem with 'down there' and never recognise that it might be a psychological problem… This study is about finding alternatives."

One 22-year-old, who did not wish to be named, underwent surgery in October. Although she suffered irritation from the size of her labia before the operation – sometimes when walking and often during sex – she admits her decision to have surgery was mostly psychological.

After having surgery on the NHS, she said it took more than two months for the pain to go away: "It was horrible. They didn't explain how much it was going to hurt. I couldn't walk for three days and I caught two infections. A lot of women who go for surgery don't know what kind of pain they are putting themselves through. I never want to go through it again, but I'm glad I did it. It really helped my confidence."

If you're seeking surgery or have undergone labiaplasty and would like to contribute to the King's research, visit www.veale.co.uk.