What is a slut? In the past, the word was used simply to mean any woman who didn't behave: a woman who was "dirty, untidy or slovenly", a slack servant girl, a woman who failed to keep her house in order and her legs closed before marriage, a woman who invited violence and contempt. Today, in a world sodden with images of shorn and willing female bodies, a slut is any woman with the audacity to express herself sexually. That should tell you everything you need to know about modern erotic hypocrisy.

On 11 June, London hosts a SlutWalk. The phenomenon began in Toronto after a local policeman instructed a group of female university students to stop "dressing like sluts" if they didn't want to be raped, a point of view not unique among men in positions of power. The protest that followed has infected the imagination of women in cities around the world, from Dallas to Delhi, who are sick of being bullied and intimidated into sexual conformity.

We like to think that we live in a liberal, permissive society - that, if anything, the problem is that there is too much sex about. This is a cruel delusion. We live in a culture that is deeply confused about its erotic impulses; it bombards us with images of airbrushed models and celebrities writhing in a sterile haze of anhedonia while abstinence is preached at the heart of government.

In Britain, the release of an official report declaring that girls are being too "sexualised" has coincided with parliamentary lobbies for young women to be "taught to say no". Join the dots with police officers telling women that "no" is insufficient if they happen not to be dressed like a nun and an ugly picture begins to form. What we're looking at is a concerted cultural backlash against female sexual liberation.

Give us protection

Sex is not the problem. Sexism is. Arbitrary moral divisions are being renewed between "innocent" women and "sluts". Young women, in particular, are expected to look hot and available at all times, but if we dare to express desires of our own, we are mocked, shamed and threatened with sexual violence, which, apparently, has nothing to do with the men who inflict it and everything to do with the length of skirt we have on. Some of us have had enough.

Faced with savage public opprobrium, told that our sexuality is dirty and dangerous, today's young women would do well to take inspiration from the gay rights movement.

For decades, LGBT protesters have marched to demand the right to express their sexuality without fear of victimisation and to show that, whatever society thinks of them, being queer is not a source of shame, a threat to innocence or an invitation to violence. Like them, sexually active women deserve protection just as much as those whom polite society considers "pure".

Some may wish to reclaim the word "slut" to celebrate its implications of bad behaviour. What's more important is that we refuse to let the word sting, or draw distinctions between "good" and "bad" women, based on outdated notions of sexual purity. Now, more than ever, it's time for "sluts" to walk - and walk tall.