When it comes to long term relationships, women go off the idea of having sex with their partners before men do, says the National Survey of Sexual Attitudes and Lifestyle.

But you probably already knew that, right?

It’s one of those things that everyone has a low-level awareness of - yet no-one had confirmed it until now. But confirm it they have. So the big question is: why?

Let's be clear - women aren’t less inherently sexual than men. Women, contrary to what you might have been told, don’t find it satisfying to grit their teeth through sex until they’ve produced children and then spend the rest of their lives faking a headache. That’s not what we want.

As a woman, newer is always better. You should be constantly working towards your 'perfect' hair colour, career and partner

But it seems that is what many of us are lumped with. The most shocking part? Just how quickly we get bored. The research found that women who had been in a relationship for more than a year were getting fed up.

Twelve months. One single year.

Perhaps it’s because of the way we’ve been socialised. We are taught to constantly reinvent and reinvest. A dress that you’ve had for a year isn’t exciting any more, you need a brand new one. Your athletic figure honed last summer? So behind the times. Now you need a massive bum and tiny tits.

We’re expected to be in perpetual motion, changing and improving all the time. As a woman, newer is always better. You should be constantly working towards your 'perfect' hair colour, career and partner. The idea of being comfortable with something static, is a totally alien one.

Trying to recapture the newness just won't work... credit: LB Images / Alamy Stock Photo

But aside from this idea that the status quo isn’t good enough - that we must improve or perish - there’s another reason why we’re getting bored of our sex lives so quickly.

Simply, there is a lingering perception that sex isn’t for women. That it’s something done to us, almost in spite of us, rather than with us. There are numerous studies which prove straight women have the fewest orgasms, and that many women don’t come from penetration alone and therefore regularly go without sexual gratification. It’s well documented that a lot of straight women have crap sex.

One of the few guarantees about sex is that the first time you do it with a new person, it’s exciting. Unwrapping them and getting to experience their naked body for the first time, discovering all the secrets that their clothes have hidden. It’s guaranteed to be interesting, even if it’s not actually good.

Similarly, the first few times you have sex - even if it’s an orgasmless wasteland - you learn exciting new things. You understand their desires and their predilections. You become a sexual anthropologist.

Don’t assume that your partner has 'gone off sex' because they’re getting older, or because they just 'aren’t that sexual'. Take responsibility for it

And then the newness wears off. No matter what we do, none of us can be new again. Lingerie, role play, threesomes: they’re all different ways of trying to achieve the same impossible feat, a renewed sense of excitement. And if all that was gratifying and exciting about the sex you were having was the newness - then what’s left?

Nothing. So of course you become bored. It’s a sort of 'catch 69' (to steal a joke from Carrie Bradshaw). The sex was fine because it was in your 'honeymoon period', so you didn’t raise your hand to say that you hadn’t had an orgasm.

But now it's familiar and you've started to notice the mediocrity a heck of a lot more, but it feels too late to be honest about how little you truly enjoyed it the first few weeks.

It’s the sex equivalent of not hearing someone’s name at a dinner party and then spending the rest of the evening making a sort of non-specific noise when you have to introduce them.

Women are taught to accept mediocre sex (posed by models) credit: Getty Images Contributor

I can’t count the number of times a man had told me that his wife or girlfriend doesn’t like sex, or has gone off sex. They discuss it as if it’s a personal insult, something that they’re suffering from. ‘Can you make my Missus want sex again?’ I’ve been asked dozens by semi-strangers in pubs and at parties.

‘I can’t’, I tell them. ‘But you probably can.’ All it really takes is an adjustment of attitude.

Don’t assume that your partner has 'gone off sex' because they’re getting older, or because they just 'aren’t that sexual'. Take responsibility for it. Open a dialogue. Find out if she was actually enjoying the sex that you were having in the first place, or whether it was actually always mediocre and just made okay by newness and desire to make you happy.

Women have a responsibility here, too. It’s lazy to accept unsatisfying sex, and it’s going to make you unhappy in the long term. Saying the words ‘Actually, I didn’t come’ might seem nerve-wracking at the beginning of a relationship, but they’re a whole lot harder to say once you’ve been together for months or years, and the first question your partner is going to ask is ‘why didn’t you tell me sooner?’

Good sex is a right, not a privilege. But it doesn’t just happen. Like the rest of a successful long term relationship, it takes work. It might not sound sexy, but it’s true.

Purchase Fifty Shades of Grey for £24.99. Alternatively, if you wish to purchase any other books, please visit the online Telegraph Bookshop or call 0844 871 1514