"Keep your mitts off our muffs!" "I love my vagina!" "You've put my chuff in a huff!" These are some of the slogans of the Muff March taking place along London's Harley Street Saturday morning. Its aim? To raise awareness of the increase in gynaecological cosmetic surgery – both on the NHS and in private clinics. The march, which has more than 300 supporters on Facebook, is organised by campaigning group UK Feminista and performance artists The Muffia, who dress up in nude bodysuits decorated with lavish pubic hair.

At its most modest, the Muff March is against the pornography-influenced obsession with removing pubic hair. But it's also about protesting against the sort of surgery that makes you cross your legs. Typical procedures on offer include labiaplasty (trimming or removing the labia) and vaginal rejuvenation (tightening – usually referred to by "designer vagina").

In the US this industry is worth $6.8m (£4.4m). In the UK the latest figures come from a 2009 report in the British Journal of Obstetrics and Gynaecology. It revealed that in 2008 the number of operations increased by 70% compared with the previous year: 1,118 labiaplasty operations on the NHS. (There were 669 in 2007 and 404 in 2006.) And that's just the NHS. The Harley Medical Group reported over 5,000 inquiries about cosmetic gynaecology last year, 65% for labial reduction.

Professor Linda Cardozo of King's College London recently warned of the risks of labiaplasty: permanent scarring, infections, bleeding and irritation. "The private sector is not recorded, audited or regulated. At least if you have it on the NHS you have to go through your GP and that's a gatekeeper." (Although one anonymous blogger writes on the NHS website: "I have flaps of skin everywhere and the whole thing is a total mess. I will never be able to be intimate again.")

I recently heard of a woman GP very concerned by the number of girls in their mid-teens coming to her worried about what their genitals looked like: she thought it was becoming an issue largely because of the fashion for shaving off pubic hair, which made them more self-conscious. Of course, there are rare cases where there is an underlying medical reason for this surgery, but they are just that, extremely rare. A doctor who has treated women seeking labiaplasty told me: "When you examine them, they are completely normal."

Some experts suggest this is a new form of body dysmorphic disorder. Others see it as a depressing but logical extension of the pornification of our culture. As it becomes more acceptable for young people to watch porn (where a "standardised" genital appearance is encouraged and many of the women have no pubic hair), so young women having their first sexual experiences are being measuring – and measuring themselves – against this weird porn "norm". As one woman who has sought surgery says: "I browsed through one of my brother's Playboys to see what the girls looked like. Some seemed to have very small or almost no labia." In a world where not even your labia can ever be pretty enough, it's time to fight back. Forward march, muffs!