When the passion died away Erica didn’t want to give up on her marriage.

She still loved her husband, but neither was she prepared to forgo a satisfying love life. Instead, after years of sexual disappointment she took an unprecedented course of action — she went online to look for a lover.

‘One day I’d just had it. I really wish I could remember what exactly caused me to search online for “someone” because that is not like me at all,’ says Erica, 46, who went on to have a passionate affair.

Georgie, aged 53 and married for 25 years had a similar experience. ‘I finally decided after many years of no sex that I deserved to have my needs met,’ she said.

Meanwhile Tiffany, 47, confessed she had also gone looking for a lover because: ‘A lack of sex drove me crazy.’ These are just some of the real women’s voices and stories I encountered when researching my new book on female infidelity — which experts believe is on the increase.

Author Wednesday Martin spoke to married women who consider infidelity for her new book. Clare Matthew, 40, (pictured) claims she was able to fall in love again after a six-week affair during her first marriage

For many, being unfaithful in whatever form is an unthinkable betrayal of marriage vows, yet in some ways these women are not exceptional. In good jobs, often with children in what they said were otherwise happy marriages, sometimes church goers, infidelity wasn’t something they’d considered before.

Their problems — unfulfilling routine sex, or no intimacy at all with husbands or long-term partners, or a craving for sexual variety and novelty — are far from unique. Crucially, none of these women wanted to give up on their marriages or loved their husbands any less.

Yet they were tempted to look elsewhere for sexual fulfilment when perhaps, in the past, they would have just put up with it.

Women like the lady in her early 60s, who told me frankly, when she learned I was writing a book on women’s infidelity, ‘I want to have sex all night long. Just not with my husband!’ Or the dozens of other women I interviewed who said a version of the same thing: ‘My marriage is pretty great. But I think about other men all the time.’

It seems more and more women are prepared to act on those thoughts and seek sexual satisfaction outside of marriage.

Women are now 40 per cent more likely to cheat on their husbands than in 1990.

Many experts suggest that in reality the figures are likely much higher, because there is still a stigma associated with women who admit to infidelity. (One study found that up to 50 per cent of women admit being unfaithful to a partner at some point.)

Men used to cheat at much higher rates compared to women — but this ‘infidelity gap’ between the sexes appears to be narrowing all the time. As women grow increasingly vocal about telling the world what they don’t want they may feel more comfortable telling the world what they do want. For many, it will not be monogamy.

Georgie, Tiffany and Erica, who took part in a recent study by sociologist Dr Alicia Walker about women looking for trysts online took a pragmatic, ‘my needs first’, approach to solving their sexual issues.

Sociologist Dr Alicia, met women who believe their needs come first while conducting a recent study. The women searched for lovers who wouldn't desire a relationship or become emotionally needy (file image)

They looked for men with the physical attributes they desired, and avoided those who seemed emotionally needy or who were looking for relationships.

If a man’s performance didn’t match up to expectations or he started getting too close they would move onto the next one without a second thought. They did the same when the feeling of exhilaration about being in a new sexual partnership faded.

Having chosen a husband or partner who did not satisfy them sexually, they were not going to make the same mistake in their affairs.

As Heather, 43, who also took part in the research, observed:, ‘I try to find men who won’t be clingy, and just want great sex.’

Some experts told me the infidelity gap is closing partly due to more women being out in the workforce. In work we have an increased exposure to potential sexual partners, more time apart from spouses, more travel opportunities (people tend to have flings when they travel), and a greater financial independence, which can make getting caught seem like less of a potential catastrophe.

In the first three years of a relationship women are twice as likely to become sexually bored

Technology may also be helping women when it comes to sexual exploration, with various social media platforms and apps affording us discreet opportunities for infidelity. But acting on your desires requires having desires.

So has there been a shift in the way women experience desire? After all, this contradicts what we’re told so often about a women’s sexuality — that it’s women who have lower libidos than men, or are the ones who go off sex in relationships.

But new research is now helping us rediscover the truth about the female libido that had been forgotten due to hundreds of years of social convention and strict morality codes that ostracised women who are unfaithful or merely sexual.

What I’ve discovered — by talking to women (aged 20 to93) who’ve either cheated on their partners or considered it, and investigating scientific and evolutionary theories — is that women’s libidos are far stronger and more adventurous than we thought.

Until recently, women have tended to blame themselves for a lack of desire. Psychologists and other experts are suggesting, however, that it’s not that women lose interest in sex per se — it’s that they simply stop being interested in sex with their other half.

Professor Marta Meana, claims women may struggle with the routine of marriage and becoming over familiarised with their spouse (file image)

Marta Meana, a professor of clinical psychology, is following 19 women in a long-term study about low desire. They are all in enduring relationships they describe as happy. She agrees the issue of a sinking libido isn’t one of hormone levels or because it’s a turn off if he doesn’t pull his weight at home, but the fact that women are just more likely than men to lose interest in the same partner.

She says: ‘Marriage itself tends to make routine what was once transgressive and sexy in ways that especially impacts women, “over familiarising” our spouses in a fashion that we struggle with.’ Meana’s work suggests we women long for and respond to lustful gazes from strangers.

Her findings and other data contradict everything we’re told about women needing intimacy and familiarity to feel sexy.

While none of her study group have actually been unfaithful she says: ‘So many women experiencing low desire in long-term partnerships know that if they did step out, their desire would probably be back “like that”.’

While we tend to assume that men like to ‘sow their wild oats’ but women search for ‘the one’ some scientists suggest that it’s women, more than men, who actually need “the new” when it comes to sex. A 2017 study of more than 11,000 British men and women, aged 16 to 74, found women who lived with a partner were twice as likely as cohabiting men to lose interest in sex.

What happens after an affair? Clare Matthew, 40, a school receptionist, is married to second husband Rob, 35, a civil servant. They have two children, and live in Colchester. Clare had a six-week affair during her first marriage. I never imagined I could be unfaithful. But when I was feeling unloved and vulnerable, I’m ashamed to admit I strayed. I had never cheated before, and I was filled with guilt. I married my first husband in my mid-20s. I expected to settle into comfortable married life, but we both had busy careers in the civil service which neither of us was prepared to step back from. Clare Matthew, 40, (pictured) decided to cheat on her first husband because their marriage was emotionless and she felt alone He was still interested in sex, but I wasn’t satisfied. It was emotionless and cold, not loving. In public he was distant and didn’t compliment me. If only he had shown some warmth I’d never have cheated, but I felt alone. I found it difficult to keep my emotions in check at work. So I wasn’t surprised when my boss, who was married, asked for a word in his office. The door closed and he pulled up a chair next to me. He asked if everything was all right. I blurted out my troubles. He was sympathetic and invited me over for dinner. My husband was away with work and I immediately said yes. I assumed it was an innocent offer, but with hindsight deep down it felt flattering that someone — especially someone good-looking — was paying attention to me. I dressed up. My affair was a confidence boost but filled me with guilt I was surprised when I arrived to discover his wife was away, but after dinner we kissed and one thing led to another. I told myself it would happen only once. But my boss sent me a series of flattering texts and I couldn’t resist. The sexually charged words made me feel desirable when all my husband did was criticise me. The secrecy was intoxicating and exciting, too — it was a huge confidence boost. Yet I was filled with guilt. My marriage limped on for another year, but eventually we divorced. I’m so happy to have met Rob and fallen in love again — and I can’t imagine everbeing unfaithful to him. Advertisement

Another survey found that in the first three years of a relationship, women were roughly twice as likely as men to become sexually bored.

One experiment led by Bio-psychologist Dr Meredith Chivers, involved men and women being shown pornographic films while their physical responses were monitored.

Fascinatingly, the bodies of women who described themselves as heterosexual responded to just about everything they saw, whether it was straight, gay or lesbian sex. Straight men, meanwhile, had narrower tastes — their bodies more predictably turned on by men and women, or women and women.

Dr Chivers, told me that not only does recent work in this area suggest that women’s desires are broader than previously thought, but that their libidos are also stronger than we’ve been led to believe.

In another experiment male and female participants watched an erotic film and then assessed their inclination to have sex.

Men and women reported almost identical degrees of desire. Another test revealed that female participants were just as turned on by the prospect of sex with a stranger as straight men were. According to Dr Chivers, the key to understanding the difference between men and women, is understanding the difference between responsive desire and spontaneous desire.

Clare (pictured) found confidence in sexually charged words from her boss at a time when her husband was regularly criticizing her

While men may experience more spontaneous desire — they can go from 0-60mph very quickly — when it comes to responding to erotic stimulation women show levels of passion that rival, if not outdo, the men.

But why would women crave variety? After all since Darwin it’s been accepted that a woman is biologically programmed to seek out one mate who can provide for and protect her while she brings up her babies.

Meanwhile men are designed to spread their genetic material far and wide. If they have affairs it’s because their evolutionary make up means they just can’t help it. Right? Yet, the latest evolutionary research turns that whole idea on its head.

In fact, some scientists now suggest that it’s women who need new experiences to keep interested because of how things went in our evolutionary pre-history.

It turns out, there are sound evolutionary reasons why we are are programmed to get bored making love to the same man and lust after others.

Forget the popular image of the fur-clad caveman going off to hunt while his woman looks after their baby, there is a growing theory among anthropologists that we evolved not as monogamous pairs but as ‘co-operative breeders’. In this way of life, loose bands of men and women raised their young collectively, and very likely mated with multiple partners.

For early humans, female promiscuity was, under certain circumstances, a smart reproductive and social strategy.

Professor Dr Lisa Diamond, says couples who do something new together often report a resurgence of puppy love (file image)

A way to increase the likelihood of getting high-quality sperm and maximizing the chance that numerous males might be willing to support her during pregnancy and protect and feed her and her offspring.

It makes a lot of sense. Sleeping with a number of men, hedged against a single partner with poor fertility, could increase chances of being impregnated at your fertile time.

There’s also a theory that the unpredictable nature of a woman’s orgasm, the female capacity for multiple orgasm, and the need for cumulative stimulation to have an orgasm (‘build up’) was biology’s way of encouraging us to have sex with a variety of men in rapid succession.

If one man couldn’t give us sexual satisfaction in a single copulatory bout, perhaps another or another few could get us there.

It may be a comfort to many despairing wives to learn that their ‘disinterest in sex’ is actually sexual boredom, and is a likely part of a woman’s biological make up — and not because they don’t love their husbands.

For centuries the script has been written for us: women — unlike men — are not meant to be sexually voracious and we’ve been brought up to believe sexual satisfaction is not something we should be actively seeking out.

As more and more women now start to assert themselves in this area of their lives, some find themselves breaking society’s taboos — whether through infidelity or exploring more open relationships.

Many more are keen to make conventional, monogamous marriages work. Dr Lisa Diamond is a professor of psychology and gender studies and she says it is still possible to keep the spark of excitement alive.

A strong predictor of desire in long-term relationships, she told me, is when couples make an effort to do something new together. ‘I’m not talking about just sex,’ she says. ‘It could be skydiving, or taking a dance class, or going on a zip line.

‘When couples participate in new and thrilling activities together, they often report a resurgence of puppy love from seeing their partner from a new angle. And the simple fact is that our partners don’t stay the same over time.

‘If we want to be monogamous, we can look for and find novelty in that same person.’

Adapted by Clare Goldwin from Untrue: Why Nearly Everything We Believe About Women And Lust And Infidelity Is Untrue by Wednesday Martin, published by Scribe on October 11 at £14.99. © Wednesday Martin 2018. To order a copy for £11.99 (offer valid to 18/10/18), visit mailshop.co.uk/books or call 0844 571 0640. P&P free on orders over £15.