They debate over when children should be given sex change hormones - which can cause infertility

Experts investigating why there's an increase in gender confused children believe it could be due to pressure to 'fit in'

to specialist Tavistock clinic in London have gone up 100 percent in the past year

Ash was just three years old when she came to her mother sobbing, not over a cut knee or a broken toy, but because she couldn't understand why everyone thought she was a boy.

'It is your fault you gave me a boy's name, that is why I am a boy,' she said. 'When are you going to take me to a doctor to have it taken off?".'

Now aged eight, Ash from Ramsgate lives as a girl, but experts warn she faces an uncertain future as the long-term implications of drug treatments - which are known to cause infertility - and surgery are still unknown.

Ash was born a boy but now lives as a girl. She said being a boy felt like she was 'telling a lie'

Ash is one of a growing number of children who have been referred to The Tavistock's Gender Identity Development Service (GIDS) in London, the only such service in the UK for children that is NHS-funded.

The service has seen a 100 per cent increase in referrals in the last year. A decade ago, they received 40 referrals a year, now that figure is up to 1,400.

The trust has trained 30 new staff since the summer to cope with the increasing number of cases.

A new Channel 4 documentary airing next week, Kids On The Edge, has been given unprecedented access to the service to meet the growing number of children referred there, and hear from the doctors and experts who help them.

Dr Polly Carmichael, a Consultant Clinical Psychologist Director at Tavistock, said a key part of the treatment process is understanding why the numbers asking for a sex change are rising.

She believes i t could be down to the fact society is more accepting of transgender people today so there is no longer a fear or stigma attached to seeking help.

Or she wonders, if, for some, it could be a misplaced sense of self, a belief that their unhappiness or ability to fit in is solely down to their gender, and if that was changed, their lives would be transformed.

Dr Carmichael said this is something they always explore as, just with anyone undertaking plastic surgery, a change of appearance will not automatically make someone happier and more popular.

Ash would like to have 'blockers' to stop her entering male puberty. She won't be allowed sex hormones on the NHS till she is 16, in case she changes her mind about wanting to become a girl - she is adamant she won't

She explains: 'If we create a narrative which is it is the end of the world if you can't fully be seen to be a particular gender, or if there are things that don't quite fit, I wonder if that is the right sort of message we are giving.

'How far are the physical changes one seeks motivated more around feeling that you fit in and are accepted by others?'

She added: 'There isn't a right and wrong and no one has the answers, it is an evolving picture with many voices contributing.

'All we can go on is the young people who have taken this route and feel it has been the right thing for them to do.'

Dr Carmichael said everyone at Tavistock works hard to assess a child's mental health and wellbeing before recommending they are given sex hormones to change their gender.

How far are the physical changes one seeks motivated more around feeling that you fit in and are accepted by others? Dr Polly Carmichael

The fact a child may later decide they would prefer to remain the sex they were born weighs on their mind, as does the long-term effects of taking such drugs.

In the last few years it has become more common to prescribe hormones to young people but there is no information about the consequences down the line.

For instance, by taking the hormones, some of the children become infertile, taking away their chance to become a biological parent when they are too young to decide if that is something they will want later in life.

The children, like Ash, are in turmoil over their gender and a feeling that they don't fit in, with some sinking so low they consider suicide.

Describing how she often never feels 'right', Ash explained: 'I feel like a regular girl but I am not. There is something inside me that is saying to come out.

'I was born a male and my name was Ashton but I say he was an older brother that died and fell off a cliff. Living as a boy felt like telling a lie.'

I was born a male and my name was Ashton but I say he was an older brother that died and fell off a cliff Ash, aged eight

When Ash was seven, she told her mother she wanted to end it all as she was being bullied at school because of her desire to be a girl.

Recalling the terrible conversation, Terri said: 'She said she wants to be in heaven, she doesn't fit into this world. She is scared she is going to die and loves me and doesn't want to leave me.'

Terri, who is separated from Ash's father, Richard, a builder from Ilford who is still closely involved in her life, moved Ash and her younger siblings to Brighton.

Ash was enrolled at her new school as a girl but they found anxiety over when her 'secret' would be uncovered too stressful, and Terri decided they would be better off back in Ramsgate after all.

Ash is one of a rising number of children referred to The Tavistock's Gender Identity Development Service (GIDS) in London. Experts there investigate why children feel so strongly about changing sex and assess the best course of action

Now Ash, along with her parents, is seeking information from experts at Tavistock on whether she could have 'blockers' to prevent her going through male puberty, as she is terrified of getting facial hair and a deeper voice.

'Blockers' can be given to Tavistock patients at the age of 11 (along with their parent's consent), essentially to buy time in case a child changes their mind about a sex change as they age.

It is the only drug that would be currently available to Ash on the NHS, as protocol at Tavistock states that sex hormones cannot be prescribed until a child is at least 16. Then at 18 they can be considered for surgery.

It is really important to be checking with people their expectations of physical interventions as it is obviously true they are not the panacea to all things Dr Polly Carmichael

Ash is confident she won't change her mind about being a girl as she gets older. She is so feminine, her mother had to check with doctors whether it was possible she could have naturally developed some female hormones.

Such is Ash's belief that she is a girl, she tells her mother she can feel her breasts growing and she can't wait till the day she will give birth to her own child.

Terri has tried to tell her daughter this may never happen because of the way she was born, but Ash replied she could have a womb transplant after reading about the recent pioneering operation in Sweden.

Dr Carmichael said part of their involvement with gender confused children and their parents is managing such expectations.

Dr Polly Carmichael works with children who want to change gender to assess the best form of treatment, but she admits even the experts don't know all the answers

'Young people can see the information available online and on social media, they can form an idea of where they want to be, yet they don't really have a full understanding of the implications of some of these decisions,' she said.

'It is really important to be checking with people their expectations of physical interventions as it is obviously true they are not the panacea to all things.'

She added that many children and their parents are desperate for a quick fix but there are no simple solutions.

'We don't really know if this is the right treatment for everyone or whether there are long term implications for this treatment but for families and young people if can be very difficult,' she said of those they help change sex.

'They are seeking certainty, but the reality is at the moment we don't have certainty.'

Kids On The Edge is on Channel 4 Wednesdays at 10pm