More children than ever are seeking specialist mental health treatment in England but tens of thousands are being turned away despite evidence of self-harm or abuse, according to a report.

An investigation by the Education Policy Institute (EPI) found that referrals to children’s mental health services in England had increased by 26% over the last five years – but nearly one in four were rejected, meaning that at least 55,000 children were not accepted for treatment in 2017-18.

Most were rejected because their condition was not regarded as serious enough to meet eligibility criteria – including young people who had experienced abuse or showed evidence of self-harm.

The report also found that even those who were accepted faced long delays in getting treatment. Children in London have to wait more than two months on average, well above the government’s target of four weeks.

“This report shows a significant increase in demand for children’s mental health services over the last five years, even as many local authorities are having to cut back on the services they are providing. This is very worrying and could lead to increased access problems,” said David Laws, the former Liberal Democrat minister who now chairs the EPI.

The difficulty in accessing services means teachers are frequently caring for young people in severe distress Anna Cole, Association of School and College Leaders

The EPI collected the data through a series of freedom of information requests to child and adolescent mental health services (CAMHS) and local authorities. Responses were received from 54 out of 60 services and 111 of 152 local authorities.

Whitney Crenna-Jennings, the author of the report, said there was little evidence of any significant improvement in access to children’s mental services, although it did find a small reduction in the very longest waiting times.

“There continues to be a significant postcode lottery in the proportion of referrals accepted into specialist care and waiting times to treatment, with long waits in some areas,” the report notes, with 188 days the longest reported.

The data showed that between a fifth and a quarter of children referred were deemed inappropriate for specialist treatment, with the most common reasons being that their condition was not suitable or serious enough.

“This bleak picture of vulnerable young people being turned away from specialist mental health services or facing long waiting times for treatment is all too familiar to schools,” said Anna Cole of the Association of School and College Leaders.

“The difficulty in accessing these vital services means that schools and teachers are frequently supporting and caring for young people in severe distress, even to the extent of having to take them to A&E because they have been unable to access timely specialist support.”

Treatment criteria vary widely between services and regions. In some cases children were turned down for support if they had not engaged with other services, if they only demonstrated difficulties at school, or if they displayed “normal” responses to traumatic events such as abuse or bereavement.

“Overwhelmingly, providers reported no or limited follow-up after a referral was deemed inappropriate – only a minority contacted other services deemed more appropriate and a small minority checked whether the young person had accessed other support,” the report found.

“The fact that self-harm is not always sufficient to trigger access to specialist services clearly signals that wider preventive services are needed.”

Paul Whiteman, the general secretary of the National Association of Head Teachers, said teachers were having to re-refer the majority of children who were turned down. “The reason given in most cases, that the problem is ‘not serious enough’, simply isn’t okay. Early intervention is vital when it comes to mental health,” he said.

“The government is taking steps to improve mental health services for children and young people, and its mental health green paper takes the right approach. But it is doesn’t go far enough quickly enough.

“New funding and training isn’t going to reach the vast majority of areas for more than five years. Children need help now.”

A quarter of local authorities said they had cut services related to young people’s mental and emotional wellbeing. Among the programmes cut were community-based early intervention services, school-based programmes to support children with mild or moderate mental health difficulties, and counselling and support for vulnerable young people.