Playing a sultry call girl while pregnant was not an easy task, Billie Piper has admitted.

The 25-year-old plays Belle in the ITV drama Belle de Jour, but told the Radio Times: 'I was eating like a horse!

'Being pregnant and filming scenes where you're having to be sexually provocative - when all you want to do is sit in a corner and eat - that was hard for me.'

Billie Piper: Producers of Belle de Jour had to use creative angles to avoid showing her growing bump

The former teenage popstar is expecting her first child with actor husband Laurence Fox before the end of the year.

And Billie, who is about seven months pregnant, said her bump was visible in the second series of Secret Diary of a Call Girl.

Baby on board: An off duty Billie pops out to the shops

'The camera and lighting crew and directors had to work a lot harder - we were shooting around my torso, basically.

'Towards the end it was really tricky - I was showing big time. I wear tight clothes in this show, so it's obvious.'

Now that filming is finished Billie plans to focus on motherhood over her career.

'For the moment I'm just going to focus on being a mum and that's kind of a relief because it means I don't have to think about... the rest of my career,' she said.

The actress joked of calling her baby Silver or Sly when it was born, adding: 'No, we're really rubbish. It's funny. You go, 'That's a nice name', then you say it aloud three times and you go, 'that's awful'.

'It's a lot harder than I thought.'

The Doctor Who star said she was intimidated by large groups of children who approach her because of her role as Rose in the hit BBC1 sci-fi show.

She said: 'The only thing that's stressful is walking down the street when schools are out. I don't know how David (Tennant) does it. Sweet as they are, kids en masse are kind of frightening.

'Every child just thinks you're Rose and you don't want to spoil the illusion. I really feel for David because that's his life - everywhere he goes is slightly chaotic.'

Billie met her husband, who comes from the Fox acting dynasty, when they starred together in the West End stage play Treats in late 2006.

The actress, who was previously married to DJ Chris Evans and remains good friends with him, is expected to start filming the third series of Diary of a Call Girl in the New Year.

At the age of 15, she was the youngest artist to debut at Number One in the UK singles chart with Because We Want To.