Imagine setting out to break up the most solid marriage. Think you're not the type? Don't be so sure. Monique, 26, always thought of herself as a serial monogamist; she had been in a number of long-term relationships and hadn't looked sideways. Not only that, she'd never for a second entertained the thought of cutting another girl's grass – until she met Martin.

I'd just moved town for work and Martin was one of my new neighbours. I instantly took a shine to him. He didn't wear a wedding ring, so when he asked me out for a drink one Friday night I had no idea he was married and hoped it was more than just a get-to-know- you thing.

“Over a few beers he told me about his life and his wife. I took it all in, but the chemistry between us was too strong to ignore. She was a flight attendant and was flapping her wings somewhere over Europe. So, with no chance of getting caught, we ended up spending the whole weekend together – in bed.

“Our six-week affair fell to bits when his wife read some text messages I'd sent him. She came storming into my yard one day, hurling abuse at me. It was humiliating for everyone involved and was the talk of the street for more than a few months.”

Monique's story isn't unique. Victoria Beckham's been standing by her man publicly since several women have alleged that they've bedded her soccer-star hubby David Beckham. From a Spanish personal assistant to a Swedish glamour model to an Aussie escort, they all knew Becks was spoken for, but that didn't deter them.

Okay, so a fling is one thing – women have been known to forgive a man for a one-night stand – but most of these women believed that they had a 'connection' with Becks and claim something a little more ongoing than a one-off lip lock.

Rebecca Loos, David Beckham's former assistant, has since launched herself on the world's media exposing all details of her X-rated affair with the Real Madrid star, even claiming she was like a wife to him.

Monique felt the same. “Sure Martin had admitted his marriage to me, but she was never around. I was and I thought that meant something. I thought that made it okay.” But it didn't. Monique now admits it was one of the biggest mistakes of her life and agrees that ultimately, it's never okay to 'steal' a man. How would you feel if the Jimmy Choo was on the other foot? “I feel like a traiter to the female population,” she says, “I'm not proud of myself.”

IT TAKES TWO

You don't have to be Posh to fend off the likes of other women preying on your man. “It doesn't matter how rich, beautiful, powerful, successful or intelligent you are – infidelity doesn't care,” says author Julia Hartley Moore in her book Infidelity: Exploding The Myths. And nor does the other woman.

Karen, 23, knows how true that is. She's young, gorgeous, has a great job and auburn hair the length of her impossibly long legs. But that didn't stop an old acquaintance 'borrowing' her husband.

“Alex and I were together for a year when I fell pregnant. He asked me to marry him and everything was bliss. I thought I had the perfect family – until he started working inexplicable hours. Turns out he was having an affair with a colleague. She also happened to be an old school friend of mine who I'd put forward for the job. Talk about an ungrateful bitch!

“But worse than that, I would never have imagined my husband going for a woman like her. She was really plain, with mousy hair and shocking dress sense. Her conversation skills weren't anything very special either. “It proved to me that it's not the women that you think you need to look out for. You know, the leggy, blonde vixen with the big, glossy pout? It's usually the women you'd never suspect.”

Karen's friend always maintained that she didn't drag Alex into it and that he made up his own mind to cheat. But just like Karen's marriage, which ended soon after the affair, once that bond was broken their friendship was never the same.

Surely Posh Spice would agree that this isn't what girl power is meant to be about. “It's a betrayal of the sisterhood and ultimately, ourselves as women,” says Amanda Ferguson, author of Life Works: Rediscover Yourself & Transform Your Relationships.

FEMALE COMPETITION

If your boyfriend ever strays, even if his eyes wander momentarily, you give him a bollocking. But mostly you blame the girl in question – whether she was a willing participant or not, she's suddenly a bimbo, a slut and a bitch. You start picking her apart to make yourself feel better.

Female competitiveness is something Rachael Oakes-Ash, author of Anything She Can Do I Can Do Better has researched intensely.

“We're told from such an early age that we must share our barbie dolls or whatever and when we're older, this type of competitiveness is partly rebellion, a kind of 'f%#* you'. Then guilt strikes and we find ourselves with our head in the fridge until 2am or under a blanket of vodka.

“It stems from the classic love triangle we experience as children. The first female relationship girls have is with their mother, their first male one is with their father. But as they start to become independent they see their mother as being in the way of their father. A lot of the intense reaction that results from female competitiveness in their adult relationships is a replica of events when they were growing up.”

Oakes-Ash also points out that men become objects in women's lives, especially when we refer to 'stealing'. “It implies ownership,” she says. “And it negates the responsibility the man has, which is why he then thinks he can get away with it.” Why wouldn't he when you're off blaming the other woman rather than him?

Oakes-Ash recalls meeting a woman who told her, “I only ever sleep with other women's men.” Oakes-Ash asked her why she did it. “When she replied that she was commitment-phobic, I pointed out that there are a lot of single men out there who are also incapable of commitment and asked why she didn't make a beeline for them instead. Women like this have to ask themselves, 'Is it about the other woman?' and 'Is the man just a tool in my competitive war?'”

“That (subconscious) thought and feeling of the other woman dethroning (the girlfriend or wife) is a false sense of power, status, security and self-esteem that derives from making his partner jealous,” Ferguson says.

Ultimately, a woman who betrays other women in this way is not happy within herself and may never be. And don't forget karma, girls – what you do to others, others may end up doing to you.

MOVE ON

When Talisa, 25, met Ed, he was in her opinion, in an unsuitable de-facto relationship. So she wrote him a letter and told him so, as a way of outing her feelings. “Initially I wasn't all that successful,” she says. “And to my shock he got engaged to her and married soon after.”

Still, they remained friends and less than a few months after he was married, Talisa got her way and ended up sleeping with him. It turned into a two-year affair.

“At the time I didn't really think of her much at all,” she says. “I thought they weren't suited and would fall apart with or without my intervention.” “There's a big difference between swooping and stealing,” says Ferguson. “When a guy has really been released by a woman – you go, girl, or someone else will. But when you haven't done your homework of making sure (be honest with yourself) that she's rejected him or it's really over – forget about it.”

And be warned, if he leaves her for you, he'll most likely bring with him the same problems that helped to ruin his last relationship. For that reason, Talisa didn't pursue a long-term arrangement with Ed. “I was happy to send him back to her,” she says. “I was unemotional about it – it suited me to only see him when I wanted.

“I eventually ended it when I met someone else. I feel bad about what I did, as I would hate it if that was happening to me, but I also thought, 'Why did I never want to commit to him?' It was because I didn't trust him. After all, he was a cheater.

“Now I feel quite possessive of my current boyfriend,” says Talisa. “That's because I know there are women out there who wouldn't think twice about going after him. I used to be one of them.”

Younger women can be persuaded more easily and can persuade themselves, that the man in question will abandon his already committed life for one with her. At any point in our lives, men can be offered a wonderful connection with us and still choose another option. It sucks, but there's nothing we can do to change their mind.

“An amazing connection does not necessarily make for a great relationship – for that, both parties must want and work for it,” says Ferguson. “The initial connection is different to the commitment and sacrifice involved in taking that to a real relationship. Not all connections are meant to develop into something long-term – a sad, but real, fact of life.”

If you think you've met your soul mate but he's currently with someone else, sit tight and wait. You've got no right to pounce unless he's truly available.