One in four children and young people referred to mental health services in England last year were not accepted for treatment, according to data, raising concerns that many are still failing to get vital support at an early stage.

Research by the Education Policy Institute (EPI) estimated that more than 130,000 of those referred to specialist services in 2018-19 were “rejected”, among them young people who have self-harmed, suffered eating disorders and experienced abuse.

According to the EPI, rejection rates have remained unchanged over the last four years, despite government commitments to address shortages in child and adolescent mental health services (CAMHS), including an additional £1.4bn investment between 2015 and 2021.

The research also revealed significant regional variations, with services in London rejecting 17% of referrals on average, compared with 28% in the south, the Midlands and the east, and 22% in the north.

Providers said treatment was not given mainly because children’s conditions were not suitable, or were not serious enough to meet the threshold. The average median waiting time to begin treatment has fallen by 11 days since 2015, but children still had to wait an average of two months.

David Laws, EPI’s executive chairman, lamented the lack of progress. “Young people continue to be deprived of access to specialist mental health treatment, despite the government claiming significant investment in mental health services over the past five years.

“Progress in improving access over this period has been hugely disappointing, and it is unacceptable that as many as one in four children referred to mental health services are being turned away.”

The EPI report is based on data collected via freedom of information requests to more than 60 mental health service providers. NHS England said the EPI’s analysis was “flawed” and it was wrong to assume that every referral should result in NHS treatment, when more appropriate support might be provided elsewhere, for example from schools and local authorities.

“The NHS is actually ahead of its target on ensuring as many children as possible receive mental health care – seeing an extra 53,000 children, teenagers and young adults last year, a 14% increase on the year before and 22% more staff in services than five years ago, against a backdrop of rising referrals,” an NHS spokesperson said.

Teachers’ leaders warned that schools were struggling to fill the gap. Geoff Barton, general secretary of the Association of School and College Leaders, said: “This report confirms what schools know only too well – that thresholds for children’s mental health services are often too high and waiting lists too long.

“It is an appalling postcode lottery which leaves schools struggling to secure the specialist help needed by young people suffering from serious mental health illnesses.”

The mental health charity Mind said something clearly was not working when thousands of vulnerable young people were still being turned down for treatment. “It is deeply concerning that a staggering 133,000 young people are not getting help for serious mental health problems,” said Vicki Nash, head of policy and campaigns.

“Whatever your age, if you have self-harmed, experienced abuse, or have a mental health problem like an eating disorder, you deserve support. Extra money outlined in the NHS Long Term Plan is welcome, to tackle decades of underfunding, but it can’t reach the frontline soon enough.”

• In the UK, Samaritans can be contacted on 116 123 or email jo@samaritans.org. You can contact the mental health charity Mind by calling 0300 123 3393 or visiting mind.org.uk