One of the downsides of being known for writing a book about my sex life is that people tend to make certain assumptions. Many conclude that I must be up for hopping into bed with any bloke who offers himself as a sexual candidate. The other frequent assumption is that, because I have written an honest account about being a single woman happy to have casual sex, I must be making some kind of lifestyle choice. "Don't you ever want to settle down?" people ask me incredulously, shocked that a woman might be content with just, well, shagging.

I don't believe this assumption is held just because I've documented my sexual escapades in print. I think the fact that I am an openly happy sexually active single woman in her early 30s somehow challenges the widely-held convention that all women my age are only having sex in the pursuit of love; that we must want to settle down with every man that we meet; and that if we are still single, we must have failed in some way.

Almost every women's magazine regurgitates this perspective, filling pages of content about losing weight, applying make-up, the latest sexy fashions, all suggesting that women should focus on how they look (rather than, say, their work) because that way they will be more attractive to men and more likely to get a boyfriend; and surely it should all be about obtaining a man - and keeping him?

Like many other women, I reject this philosophy. One of the reasons I wrote about my sex life was to try to challenge this viewpoint and be able to say: I don't need validation about my attractiveness from a man to feel good about myself; I don't need a partner to be happy; and I can enjoy sex purely for pleasure. I don't think any of this is particularly revolutionary - and there are many more important battles for women to fight - but it still bears repeating. Women are still surrounded by a 1950s-style old-fashioned and sexist ideology which is that to succeed at and be happy in life, we need to be in a long-term relationship with a man (omitting the existence of lesbian relationships, of course).

Women like sex, just as men do. Not all of us expect, or want, to be given cuddles or kittens every time we shag someone. There does not have to be romance involved with sexual pleasure: some of us just like orgasms for the hell of it. And some of us enjoy having sex with someone who is not a long-term partner. God forbid you're a woman who might enjoy shagging a bloke for just one night, because then not only are you seen as a failure in life, but you're labelled a slag too. It is 2007 - we don't seem to have made much feminist progress, do we?

There is still a huge double-standard when it comes to sex and gender. Men are still slapped on the back for their achievements, rewarded for their accomplishments and applauded for their sexual dalliances. Women, however, are forced to live out their lives with frustrating and oppressive restrictions, where they are still chastised if they do not pursue marriage, children and monogamy as their main life objective.

It still shocks me that the term "career woman" exists, with no counterpart for men; being ambitious with one's work or not pursuing romance still has a stigma attached if you are female. I'm not advocating casual sex as some kind of equivalent life-vocation, though; it's fun and serves an enjoyable purpose and that's great. I'm just trying to say that to pursue it does not mean a woman has failed in some way or that she's made some lifestyle choice; it means she has an active healthy sexual appetite, which is no bad thing.

I don't wish to suggest that my own personal enjoyment and pursuit of casual sex means I have no wish for a partner at all; I enjoy the companionship of a man and think a partner would be a nice addition to my life, should I meet that someone special. But I refuse to subscribe to the notion that as a woman I cannot be happy without a man by my side; I believe it's important that as women we challenge this limited and sexist notion. Women should be able to enjoy their lives, their careers, their friends and their relationships without being derogatorily labelled. And if this means a few shags and plentiful orgasms along the way, then surely that's just a decent and enjoyable bonus?

· Zoe Margolis's book, and blog, is Girl With a One-Track Mind