Children aged as young as 11 are calling Childline in record numbers to say they are unhappy with their gender, new figures show.
Data released by the National Society for the Prevention of Cruelty to Children (NSPCC), which runs the children's helpline, shows it held 2,796 counselling sessions in 2015/16 - an average of eight per day - with children who felt their biological sex was wrong.
Session numbers have more than doubled since Childline first began recording figures on transgender and gender dysphoria issues in 2012/13, when 1,102 sessions were held.
Counsellors held more than 260 sessions with 11-year-olds. The most common age range for calls was from those aged from 12 to 15.
Homophobic bullying, which included transphobic abuse, was mentioned in 450 of the sessions.
According to Childline, young transgender people said they had suicidal thoughts, had self-harmed or suffered from mental health issues. This was often prompted by abuse and bullying.
Peter Wanless, chief executive of the NSPCC, said: "We cannot call ourselves a modern society if we stigmatise children just because they feel different.
"It is vital that children have support otherwise, as they tell us all too often, they suffer. When a child is made to feel ashamed about who they are, it can trigger serious mental health issues and crippling shame.
"It's vital young people are confident that if they speak out, they will be able to try and navigate these confusing and complex feelings without also having to fight prejudice and abuse.
"Adults must support a child as they explore what they're feeling and guide them to get the right help when necessary."
In 2014, a survey found that 48% of trans people under 26 said they had attempted suicide, and 30% said they had done so in the past year, while 59% said they had at least considered doing so.
The research was conducted by mental health charity Pace and included interviews and a poll of more than 2,000 people in England from 2010 to 2014.
One 16-year-old boy who identified as a girl told Childline: "I hate my body and feel hopeless and frustrated by mental health services. It's really difficult to talk to my parents as they just don't understand. I can't cope with another year like this one."
Young people also described feeling "trapped in the wrong body".
A 13-year-old girl who identified as a boy said: "I'm being bullied on my social network account about being transgender and it's awful. They constantly send me hateful messages and tell me to kill myself. I think it's someone at school as they seem to know things about me. I have tried blocking them but they make new accounts so I just can't escape it."
A 15-year-old boy who identified as a girl told a Childline counsellor: "I came out as trans last year and wish I'd never said anything. People shout at me every day and call me stupid and ugly. I can't cope any more and I wish I could escape from everything."
A Government spokeswoman said: "Children should be able to be themselves and all agencies have a role to play in supporting them as they discover who they are. That's why the NHS is investing an extra £2.2 million in gender identity services for young people, alongside an additional £250m a year for children and young people's mental health services - and we are investing £2.8 million to help tackle homophobic, biphobic and transphobic bullying in schools."