Hannah Bonser, who stabbed a 13-year-old to death in Doncaster, is reportedly living as a man named Adam at HMP Low Newton

A female child killer is living as a man at a women's prison, where the murderer has been boasting about an upcoming sex-change operation on the NHS.

Hannah Bonser, who stabbed 13-year-old Casey Kearney to death, has changed her name to Adam while serving time at HMP Low Newton in County Durham.

Sources say the 31-year-old's gender switch has angered fellow inmates on the high-security F Wing.

Guards now address the wing's prisoners as 'ladies and gentleman' instead of just 'ladies', according to a former inmate who said: 'It's put an end to the call of, "Cells, ladies, please".

'Hannah now insists they use "ladies and gentleman".

'Hannah's not physically a man yet, but is on her way. She has asked to be called Adam and changed her name with officials. She says she is going the whole hog.'

The move has led to accusations of preferential treatment at the prison, where serial killer Rose West and Baby P's mother, Tracey Connelly, are also serving time.

Casey Kearney was stabbed to death when she was aged just 13 by Hannah Bonser, who is reportedly living as a man in prison

Bonser was locked up in 2012 after stabbing her teenage victim as she made her way to a sleepover on Valentine's Day.

She was jailed for life and will serve a minimum of 22 years after her victim died from a single stab wound after the attack in Elmfield Park, Doncaster. The teenager managed to call 999 before she died.

Bonser, who had a history of mental health problems, had repeatedly informed medics that she thought herself to be dangerous.

Bonser is serving a 22-year sentence after she murdered a 13-year-old child by stabbing her to death while she was walking to a sleepover

Just one month before she murdered Casey, Bonser told professionals that she was worried she would kill and said her fear caused her to stay away from people on the street.

Bonser first became known to social services when she was just nine years old after the death of her morbidly obese Mormon mother. She was then referred to 16 psychiatrists and 20 mental health workers.

The future killer was hearing voices and speaking to rocks by the time she was 17, developing an obsession with druids and a belief birds were people coming to get her.

A Prison Service spokesperson said: 'We do not comment on individuals.'