Getting to grips with PVC outfits, cracking a whip and simulating sex with strangers was never going to be the easiest way to earn a living.

And after playing a prostitute in The Secret Life Of A Call Girl, gorgeous Billie Piper admits the racy role could have made her quit acting altogether.

In an exclusive interview with The People, Billie reveals: "There were times during the filming of Secret Diary when I wanted to give it all up.

"Every day I was going home from filming, putting my hands over my face and saying to myself: 'Did I really do that today? Did I really sit astride this guy, in stockings and a bra, and ride him like a racehorse, him with a bit in his mouth?'

"I did and I know this is taking my career into a new area that is going to shock people."

The former Dr Who star, who admits playing high-class hooker Belle in ITV2's new drama gave her a £1,000 lingerie fetish, not only had to be word perfect but noise perfect too during the lovemaking scenes.

She explains: "Belle really enjoys her work and that means I have to sound passionate during the love-making scenes, rather than just go through the motions.

"Anything less than total enjoyment and I'm in trouble. I run the very real risk of having to overlay the sounds several months later, in some recording studio in Soho, in front of a bunch of grinning, geeky guys.

"And, quite honestly," says Billie, 25, "sounding sexually passionate in front of people you don't feel particularly comfortable with is the last thing I want to do."

Thankfully, Billie managed to avoid her trip to Soho.

"We were blessed with an excellent sound technician, John Hughes, who recorded everything that he needed to record when we were filming and for that I am enormously grateful," smiles Billie with a sigh of relief.

Getting her "sex noises" right was just one challenge the former chart-topping pop star faced when she agreed to star in Secret Diary Of A Call Girl, adapted from the diary of London prostitute Belle de Jour.

"I was worried about what people would think if I took on the role - and I'm still worried now! This part was never going to be just about me, it was always going to be about me and the people around me.

"My dad, for example. He's a builder, who goes to pubs, to building sites, around Swindon, and I always knew that having his daughter playing a semi-naked prostitute was going to leave him open to ridicule and mickey-taking from the guys he meets. So I sat down with him and had a long, long chat and he was very supportive of what I wanted to do."

Billie also had a long chat with her actor fiance Laurence Fox, 29, with whom she shares a cottage in Sussex.

"I'm fortunate to have a partner who is in the business who wasn't going to be shocked by the idea of his girlfriend being seen naked and semi-naked on screen. Some boyfriends might have had serious reservations but he knows the business, he knows that it's part of the work.

"But I also know this is quite a change for me. There's an audience out there who know me as Rose Tyler in Doctor Who and this series is a total departure from that."

One of Billie's initial fears was that her loyal band of fans might think she was a bit too keen to play a hooker!

"I didn't want people thinking I'd been over-eager to land the role. I thought if people got the idea I'd been too keen to play a prostitute they might think I was a slag and that's the last thing I wanted to be labelled as.

"But I never had any doubt that I wanted to play Belle. Boring for me is playing the same part over and over again. Exciting for me is playing someone like Belle, who is a strong, fascinating person.

"Although she has always kept her identity secret, I was lucky enough to meet her, when I was preparing to play her, and she's one confident, cool sassy lady who gave me an awful lot of insight into being a prostitute.

"Did I learn much? Loads! Did she teach me any tricks? A few, some of which I've brought to the screen.

"But what really amazed me was what she said about her clients. Because they are the people paying the money, I imagined they would be in charge.

"But Belle says many of them are so nervous, so timid, in the presence of a powerful and confident woman like her, that they can barely talk. And some of them - to put it delicately - are too nervous to perform."

Viewers will see Billie living out all kinds of male, sexual fantasies, as Belle. In one episode, she dons a tight-fitting PVC suit and whips her client until he's begging for mercy.

On the day of the whipping, Billie admits she got more into the part than she had planned...

"I was hot, because turning the air conditioning on would have ruined it for the soundman, I found the suit uncomfortable and I was getting angrier and angrier, which I do anyway when I'm hot and bothered.

"I'm afraid I took out my anger and frustration on the guy playing Belle's client!

"Hopefully it will look totally believable on TV though I apologise, belatedly, if I caused this poor guy any real pain.

"One of the tricks that the real life Belle taught me was how to whip somebody and not bruise them.

"But I was so angry that day, it wouldn't surprise me if I'd given the guy a couple of king-sized bruises!"

Billie, ex-wife of Radio 2 DJ Chris Evans and a chart topper at 15 with the single Because We Want To, has a more permanent reminder of her stint as Belle.

Far more attractive than a couple of bruised buttocks, her wardrobe is now crammed full of sexy lingerie!

"I've discovered a previously hidden passion for beautiful underwear and I've racked up more than £1,000 worth!

"I find it pretty near impossible to walk past Agent Provocateur, now, and not pop in and buy something. They do this gorgeous pink lingerie, complete with the most beautiful bows, and I can't resist it. I have one set - I have to go and buy another!

"And what I really love is wearing it and people around me not realising I'm wearing it.

Wearing secret, sexy underwear is just such a turn on and also a total surprise. "I am, by nature, a real tomboy - or at least I was before Secret Diary.

I was a jeans and T-shirt, kind of woman, but now I am spending hours in the hairdressers' chair and hours too buying lingerie.

"It's incredibly expensive and incredibly time consuming and I've got to snap out of it before I go bankrupt!"

As well as reclaiming her tomboy roots, over the next few months, Billie is also planning her wedding to 29-year-old Laurence, the Lewis star and son of Day Of The Jackal actor James Fox. The ceremony is rumoured to be scheduled for Christmas.

Billie, who wears her three diamond engagement ring coyly said: "I can confirm that we are due to get married and we have named the day. But that's all I'm saying about our future plans!

"But of course we are very happy. Laurence is my rock." So much so that Billie seems ready to start a family. "I'm terribly broody," she explains.

"I haven't always been, because I've got two sisters and a brother, and they're a lot younger than me and I took care of them a lot.

"But back then I thought, you know, I can't imagine having a child, and only now I really can. I can feel it, it's strange."

Kids aside, she's going to wait for the fallout from Secret Diary before deciding on her next career move.

"It will be difficult deciding how to follow that.

"Remember that very beautiful model from the 1960s, Jean Shrimpton? She quit the rat race to run a hotel in the West Country - that suddenly seemed like a really attractive option while I was filming Secret Diary.

"The pressure - a lot of it self-inflicted - was immense and the stress considerable.

"But I wouldn't really have done it, I wouldn't really have just turned my back on it all. I took a couple of years off, when I finished singing, and went round the world so I've already been there and done that.

"Acting is at the heart of my professional life, now, and I'll carry on doing it - regardless of what people think of me in Secret Diary Of A Call Girl.

"But it would be naive of me not to expect a big backlash. I'm sure there will be feminists, out there who will hate it, who will think I am glamorising prostitution. I'm not. I'm just telling a fascinating woman's true-life story.

"And, in the end, when you're playing someone like Belle, you can't do it half-heartedly. You simply have to say: '***k it, I've got to go for it.'

"You've got to show your body, you've got to dress in sexy underwear, for hours at a time, you've got to perform sex acts - you've got to be naked and semi-naked in front of people you hardly know.

"That's what a prostitute does and that is who I am playing.

"I just hope and pray that people like, or at least respect, what I've done - and that my dad doesn't get too much grief when he's drinking in his local!"

'I'd go home from filming and think, did I really sit astride a guy, in just stockings and bra, and ride him like a racehorse?'

Source: The People September 2007