A five-year-old boy has returned to school as a girl in one of the youngest cases of child gender transitioning in the country.

The head teacher of the Nottinghamshire school has written to parents and classmates to inform them of the boy's wish to be treated as a girl.

It is one of the youngest cases of gender dysphoria being officially recognised in a child in the country.

Bernard Reed, trustee for the charity Gender Identity Research and Education Society, said children as young as two could express discomfort with their biological sex

The condition can be diagnosed if an adult or child identifies as being opposite to one's biological sex.

The Nottinghamshire case comes as the number of young people being referred has risen by more than 50%, according to the Gender Identity Research and Education Society.

Bernard Reed, trustee for the charity, said children as young as two could express discomfort with their biological sex. He said one in 100 people had some sort of 'gender variation' whether formally diagnosed or not.

He added it would not be until at least 10 when a child could begin taking 'puberty suspending' medication if required.

Speaking to the MailOnline he said: 'We are delighted to see the support provided for this young person by the family, the school and the authority.

'There are a rapidly increasing number of young people uncomfortable if asked to explain who they are.

'Society generally is understanding, respecting and supporting these young people which is a very welcoming development.'

He added schools were generally good at supporting children with gender dysphoria and having discreet conversations with parents.

The Nottingham Post has reported that the five-year-old girl's parents, who wish to remain anonymous, are receiving help and support.

Colin Pettigrew, corporate director for children, families and cultural services, at Nottinghamshire County Council, said transgender is a new area for many schools

Colin Pettigrew, corporate director for children, families and cultural services, at Nottinghamshire County Council, said: 'Transgender is a new area for many schools. Nottinghamshire's achievement and equality team continues to support head teachers on a range of equality issues which includes providing appropriate advice and guidance.

'Transgender is a characteristic protected by law and therefore head teachers across England continue to and are required to agree a clear plan to support the needs of transgender children and young people.'

There is only one specialist clinic in the country for young people with gender identity issues in the country, based in London.

Gender Identity Development Service (GIDS), in north London, sees children up to the age of 18.

In December, MailOnline reported on Kerry McFadyen who is helping her son who identifies as a girl.

The 32-year-old was bathing then three-year-old Daniel, who is now Danni, when he said he wanted to cut off his penis so he could be a girl.

It led to his parents making the difficult decision to allow Daniel to become Danni, in what is believed to be the UK's youngest case of a child wanting to change sex.

Kerry McFadyen pictured with Danni, who was born a boy but has lived as a girl since age three

Mermaids, a charity which supports children with identity issues, has said that up to 80 children as young as four years old are now trying to change their gender.