Vulnerable children with learning disabilities are stuck in mental health hospitals for long periods and in poor conditions, the Children’s Commissioner for England has warned.

A report published on Monday said children were spending months and years unnecessarily in institutions that are often far from their homes, while some were routinely restrained or sedated.

The number is also rising, with 250 children with a learning disability and/or autism recorded as being in a mental health hospital in England in February 2019, compared with 110 in March 2015.

Anne Longfield, the commissioner, said: “For many of them this is a frightening and overwhelming experience. For many of their families it is a nightmare.

“The onus is now on ministers, the NHS, the CQC, Ofsted and local authorities to make sure that these most vulnerable of children are not locked out of sight for years on end simply because the system is not designed to meet their needs.”

NHS figures showed that on average, children with autism and/or a learning disability had spent six months living in their current hospital, and eight months in inpatient care in total.

Although they could have returned home if support had been available, about one in seven children had spent at least a year in their current hospital spell.

A mother of a teenage girl in hospital told the commissioner’s office: “She’s been in for two years and she’s got to stay there until they find her a place.

“She doesn’t need to be in the hospital any more but she’s not allowed to come home. We would like her to be somewhere close to home that we can see her whenever we want and that she’ll be safe, where no one can take advantage of her.”

Data provided to the commissioner’s office revealed that 95 children were staying in a ward more than 31 miles from home, while nearly a third of children were in a ward more than 62 miles away from home.

Longfield’s report found that 75 children with a learning disability and/or autism were recorded as having been restrained a total of 820 times in December 2018.

One girl told the Children’s Commissioner’s Office: “I don’t like when they restrain me in my room … when there’s more than two people in my room … I get restrained with an arm around my back … It strained my wrist and it felt numb and had lumps.”

Physical restraint was the most common type, accounting for three in five interventions, while there was some evidence from children that seclusion had been used not as a last resort but as a threat.

The report also highlighted the varied quality of care in hospitals, with one family saying that their son had not been washed for six months while in hospital.

It also noted that children’s care was not being regularly reviewed, with one in four children not appearing to have had a formal review of their care plan within the last 26 weeks, according to NHS data.