Jackie Green, the youngest person in the world to change gender, is looking to get a world first by winning the Miss England title.

Green, 18, changed sex at 16 and in a new BBC documentary, Transsexual Teen, Beauty Queen, she looks to become a role model for other young people struggling with gender identity disorder by winning the beauty pregnant.

She was born Jack and the documentary explores her past, showing how her family coped with her belief that she was born in the wrong sex.

Green said: "I've always been a girl, but I had this little birth defect - like having a mole you don't like.

"I have a girl's brain but I had a boys bottom half. If you tried to dress my brother when he was three or four in girl's clothes, he would've been mortified.

"Part of you always knows. When I was four I said to my mum 'God's made a mistake. I should've been a girl."

The documentary shows how Green made the social transition to female when she was just eight, and how this led to her being bullied at school and to the brink of suicide.

Her mother, Susie Green, said: "Obviously any parent faced with a child saying that thinks 'I really want this to go away, I really don't want to have to deal with this'.

"The first time I ever took her shopping, I took this little boy shopping. We were in the girls' aisle and he was picking up dresses and putting them against himself and swirling around. I thought everybody in the shop was looking at me and thinking 'what is that woman doing?'."

After a doctor in the US helped block the onset of male puberty, Green set her sights on becoming a model, starting off by taking part in student fashion shows.

She was scouted by a modelling agency and picked in an online poll to be entered for the Miss England competition - without voters knowing she was born a boy. Green said that while the competition will help to further her career, it also serves to raise awareness of gender identity issues.

She said: "When I was young, all I'd see were drastic trans people who'd left their kids and wives. It's quite daunting to see that that's how your life might turn out. I like this idea of being a role model - but feel a bit big-headed whenever I say it."

Since being entered into the Miss England competition, Green's story has circulated across the globe and she has been the subject of tabloid attention.

"Sex change, sex swap, I f*****g hate those terms. I think it's because it's always that those words are sensationalised," she said.

The BBC3 documentary at 9pm will show how Green copes when pitted against some of the most beautiful women in England.