Is topless sunbathing over? It certainly is in France, according to French Elle, if the coverline on its new summer issue is to be believed: "La Fin Du Topless Sur La Plage?" – which translates, verbatim, to "Is this the end of toplessness on the beach?"

According to the magazine the answer is "yes", and the reasons are threefold. First, an increased concern over health and the dangers of skin cancer; second, the "pornified" perception of topless women (indeed Elle suggests the death of the monokini – ie swimming briefs – was linked to the idea that topless women are seen as "loose"); and third, the rise of breast-affiliated activism – chiefly Femen, who use their naked breasts as a means of attracting attention to various causes, and Free the Nipple, a recent campaign that encourages women to go topless to end the stigma surrounding female bodies. "Topless sunbathing was seen by women as a new freedom in St Tropez in the 1960s," says Elle. And now that they're covering up? It's a "worrying sign of a regression in the place of women".

Ever since Brigitte Bardot took off her top on the French Riviera in the 1960s, the correlation between topless sunbathing and women's liberation has been entrenched in French culture as a sign of true equality. Many others followed suit and the breast and beach were reclaimed. News that so few women are now going topless (just 2% of women under 35 said they did) seems extraordinary – and depressing.

But, according to two French women, it's more than a fear of skin cancer and political activism that has kept them covered up.

Alice Pfeiffer, an Anglo-French journalist in her 30s (who, incidentally does sunbathe topless in Biarritz, Guéthary, Monaco and surfing resort Hossegor), thinks the decline is inextricably linked to social media: "Young women in their 20s do it less because they are aware that … you can end up topless on your own Facebook wall."

Pfeiffer blames "pop-porn culture – Miley Cyrus to American Apparel, ie aggressive naked imagery of young girls" – for the shift in perception of going topless.

"Globalisation and Americanisation of women's portrayal and sexiness in France has pushed away gentle (and generally harmless) French eroticism towards porno, frontal, hyper-sexualised consciousness," she says. "Nudist, beach-like freedom is not what it used to be … breasts no longer feel innocent or temporarily asexual."

Though probably universal, this attitude towards topless sunbathing has had the biggest impact in France. It is still the norm in Germany, according to one recent survey, which suggests almost a third of Germans and Austrians sunbathe naked. A straw poll in the UK also suggests it's still de rigueur: one in six women we asked said they have or would sunbathe topless: "I don't think about skin cancer or being photographed or activism when I go topless," says Jess, 32 of north-west London. "I just want an all-over tan."

Valeria Costa-Kostritsky, a Paris-based writer, is 32 and sunbathes (not topless) in Britanny and Côte d'Azur. She says the change hasn't happened overnight: "I've never seen young women doing it loads. But some women over 50 do."

Pfeiffer agrees that the shift has been generational: "Family albums here can be a strange thing, as you flip through three generations of bourgeois bra-less women." But she maintains that "French women of most ages have, as far as I can remember, sunbathed topless."

What of the links between breasts and activism? Nudity as a political statement is no new thing – indeed, proverbially speaking, the personal has always been political – but, thanks to the internet, it has become a mainstay in the world of political activism: in France "showing your breasts wisely (a dodgy street will always be a dodgy street, so you have to act responsibly) can be a political statement," says Pfeiffer.

Costa-Kostritsky thinks the decline could be linked to health concerns, but these are less about skin damage and more about vanity: "Women of my generation have always been told that the sun was bad for our skin. But add sun damage to gravity and the fear is you won't have pretty breasts."

Pfeiffer agrees: "The ones who do it all look the same – slim and small breasts, which contributes to keeping a social order and aesthetic norm in place."

But both agree that the issue is not one of self-consciousness. "[French women] feel comfortable doing it!" says Pfeiffer. The real reason French women cover up, says Costa-Kostritsky, is because "it makes uncovering them for a lover more interesting".