The ITV drama The Secret Diary of a Call Girl, which has been commissioned for a second series despite terrible reviews, brought prostitution into the mainstream - and with it a lot of controversy. The makers of the programme, which was adapted from the book and blog by "Belle de Jour", the pseudonym of a supposedly high-charging escort, were accused of glamorising prostitution and portraying an unrealistic image of the sex industry. "It is highlighting in a big way a very tiny segment of the industry," says Karen, who wanted to talk to the Guardian about her experiences in light of the hype surrounding the programme. "The majority of what this industry is about is a lot of pain, misery and distress. It annoys me that the media like to highlight only the prostitutes who say how empowering this is. There might be a few out there who think that at this moment in time, but that is not true for the vast majority. What pisses me off about [Belle de Jour] is that you're very rarely going to have a client that you like having sex with. You have to learn to disassociate your body from your mind which is dangerous for your psyche. For the vast majority of prostitutes, it isn't glamorous - it is damaging and dangerous - yet it seems to be promoted as some kind of career option."

It is hard to understand why a woman who isn't a drug addict would become a prostitute, but then there are a huge number of reasons why someone finds themselves in this situation, says Karen. In her 20s, she was the victim of a horrific attack and sexual assault, which left her with an anxiety about men. She thinks she has tried to counteract it by putting herself in what she sees as a position of power over them. "I'm the one in control, they're paying me. I'm not stupid - [the assault] probably does have something to do with proving to myself that I can be the one in control, that I can have something at the end of it. I can say when he walks out the door."

She came to prostitution late - she is in her early 50s but looks much younger - after leaving her full-time job as an administrator six years ago after being bullied. It left her depressed and unconfident. She has a history of alcohol abuse and also had ME, which left her unable to get another full-time job. "Just driving to work and back every day would exhaust me," she says. "I have to factor in a lot of rest in my life. I know my limitations and I keep within them as much as possible."

A few years earlier, Karen had left an unhappy marriage and began using internet chat rooms to meet men. "I started going on blind dates and it slowly started to evolve into having sex with strangers," she says. It wasn't such a huge leap, she says, into charging for what she was giving anyway. "I had a bad month, financially, as I invariably would, and it started as a trickle. I had always been curious about doing it - I think I was trying to prove to myself that actually prostitution was OK. But now I realise that it isn't." She put an ad offering massage in a newsagent's window and found that sex work would fit in around the hours of rest she needed to control her chronic fatigue. "To keep myself going and pay my bills and save for my pension, I probably need to see five a week," she says. "I can almost control my workload. The most I've ever seen in one day was three. I don't have a stream of men coming." She charges £130 an hour - it used to be £170 but the influx of eastern European prostitutes, charging low prices, has pushed prices down.

For a while, Karen worked for an escort agency in London. "You got the best-paid jobs through the agency in London, but the woman who ran it would take 30%," she says. "One guy one night wanted me at 11 o'clock and I left at two in the morning. He ended up giving me £1,500. But these are the exceptions. Another guy paid me an extra £700 for unprotected sex - I walked out of there with £1,200. It was a godsend because I wasn't working much at the time." She never agrees to unprotected sex now. "I don't provide anything that's unsafe and it is probably pretty basic compared to some women out there. The more desperate you are, the more you're going to put yourself in danger."

She left the agency because she was angry at how much money the proprietor took. She tried working in flats used as brothels, but these jobs never lasted long. "One Christmas I was getting really desperate so I asked for work at a flat. It was dirty, they took out money for maid service, commission and cleaning, so I only got about half the money I earned. I'd rather work away from home, but you don't get the money and you're in somebody else's control. If I really can't face it I just won't answer the door. I'm lucky I can control that."

An estimated two thirds of prostitutes have experienced violence from clients. Has she? "Nearly. When I first started, I got trapped on a building site with a client. He locked me in a Portakabin with him. He made it clear that all the security guards had gone home because it was a Sunday evening. I hadn't realised that he was very drunk. He started talking about wanting a threesome and I said I'd ring my friend and ask her to come over. I rang this made-up number on my phone and pretended to speak to her, then I told him I had to go out and meet her. He let me out." Once she was out of sight, she ran and ended up having to climb over two 8ft fences. "Another time, I had one guy who kept insisting that I have anal sex but I wouldn't. He became extremely violent - he kept grabbing my hair and pulling it back. And you have to act like you're enjoying it. How that cannot damage somebody is ... you don't know what they're going to do if you say stop."

Then there are the scammers and time wasters, the ones who ring her up and ask what she is wearing so they don't have to ring a premium-rate phone line. "I had one man who came round and said he would only pay if he could see what he was getting. I undressed in front of him and he said, 'You've got a great body for your age, but I could go into London and pay the same money for a girl that looked like a model and was 25.' I said, 'Fine, off you go then.' I made him leave but it was so demeaning.

"You're going to get creepy men. That's a fact. I've had clients who have made my life hell. One guy came in and foolishly I didn't ask him for the money first." Afterwards, he claimed to have forgotten his wallet and Karen kept phoning him about the money. He turned nasty and threatened to burn her house down, then he started harassing her and would come by at two in the morning or would ring from different numbers pretending to be someone else. "You have to be careful not to piss someone off," she says. "Most of the time I would say the men I meet, when I have sex with them I feel neutral about them. I don't fancy them but they don't repulse me either - they're just middle of the road. Some men have actually turned my stomach - I could hardly bear for them to touch me and those are, generally, the ones who find it hard to find someone who will see them again, so they start to pester you."

What sort of men visit her? A lot are older, "Either whose wives have gone off having sex with them or they want to prove to themselves that they can still turn a woman on. They seem to block out the fact that having to pay a woman to do this kind of cancels that out. Some men are quite upset that you don't enjoy it, but those are the few. Some people say that prostitution is actually a man paying to rape a woman." Does she believe that? "I think that is true in a lot of cases. Although it is a business arrangement, he is getting off on the fact that the woman doesn't want it. Basically you've consented to being raped for money."

Even in the past couple of years, Karen says she has noticed changes in the men who come to see her and what they expect. "I've noticed that the paedophile scenario has started creeping in. Recently, I had a man who said, 'I'd like to try a 14-year-old. Can you find me one?' I've been asked to include another woman - that's quite a new thing. Two years ago, I remember men who would be upset at the idea that a prostitute they were using had been trafficked. Now I don't think it bothers them. The desensitisation process doubles up on itself every year. They want to tally up what's going on in their heads with your body. Sometimes they're not even looking at you." How does that make her feel? "Sometimes I think, it's just a performance. But it's not, it's more than that and it's very harmful."

How does she think it has harmed her? "That word disassociation comes back. I know the difference between sex for money and sex with someone you love, but if I was younger it might have damaged me more. You become hyper-vigilant. You worry about who is going to walk through the door or if the client is going to turn nasty. There is the constant worry about money."

Karen would like to be able to stop working, but doesn't know what else to do (she is waiting to hear whether or not she will be able to claim disability benefit). Would she ever be able to have a "normal" relationship with a man? "Even if I found a man I could tell what I've done, at the back of his mind he will not trust me. It puts you in quite literally a no-man's land. I will never trust a man again. In fact, I'm almost glad that I have done this because I know what men get up to. Their wives don't know. The likelihood, if you've got a boyfriend or husband, of him cheating on you is probably quite high." When I tell her I don't really believe this, she looks at me as though I'm stupid.

She calls herself as a feminist, but how does she square that with being a part of the sex industry, perpetuating it? "When I first started, I thought I was getting my own back. Men were meeting me and expecting sex for nothing so I thought, why not make them pay? It does bother me that I am perpetuating it but I don't know what else to do. I try whenever possible to counteract that with clients, in subtle ways. For instance, when a man asks me to be with another girl I say, 'Well, would you go with another man?' I try to make them stop and think."

She describes what she calls the "surround sound" of pornography - on television, in advertising, on the internet, in pop videos. "Younger women are being coerced into valuing themselves by what they look like and men's definition of how a woman should be valued. It's like being at the top of a hill and looking down and I can see all the little cultural landmarks, like the launch of Playboy, the internet, music videos celebrating a 'pimp and ho' culture, lads' magazines, burlesque. Women are being told that their bodies should be accessible at all times to men. I believe there is a conspiracy to turn women into readily accessible semen receptacles. Men are twisting this now to make women think it's a level playing field and it's equal and liberating. No, it suits men, it's convenient for men. That's what is so insidious".