Residents of the Village Naturiste in Cap d'Agde are used to going about their daily business in the nude. The fenced-off resort on the Mediterranean has its own marina, restaurants, boutiques and banks where locals can strip off and enjoy life "in harmony with nature".

Today, however, Europe's largest nudist colony has a more prudish message for over-enthusiastic visitors who are upsetting the natural order of things: no sex, please, we're naturists.

According to unhappy locals, "an explosion of libertarianism" is turning their 40-year-old resort into the "European capital of debauchery" and an "open-air brothel". Their anger is directed at an influx of foreign nudists with, they claim, only one thing on their minds. The newcomers, they say, are more interested in orgies and naked exhibitionism.

Among the worst culprits, say villagers, whose numbers go from 300 in winter to 40,000 in the high season, are Italians. Local naturists, including many grandparents, said they were "shocked" by the sight of couples copulating in public.

For Florence Denestebe, 35, a local councillor, this is the culmination of years of conflict between traditional naturists and a new generation of sexed-up nudists. "I'm not puritanical, but this has gone too far," the mother-of-two told the Observer.

"I have nothing against the naturist village with its philosophy of people living in harmony with nature, but people practising sex acts in public are giving the Cap d'Agde a bad reputation. There are places for this sort of thing – namely behind closed doors."

Denestebe said naturists made up only 5% of the population. "I'm standing up for them because they are fed up but I'm also representing the other 95% who are fed up with the bad reputation our home now has."

Cap d'Agde naturists interviewed by journalists spoke of witnessing orgies, voyeurism, fellatio, genitals being "waved in people's faces" and people being tied to signposts and whipped.

Denestebe is writing to the state prosecutor demanding public decency laws be upheld.