Up to four in five children with mental health problems are being denied access to treatment they urgently need in some parts of England, NHS figures show.

Overall six in 10 children and young people across England do not receive treatment for problems such as anxiety and depression, despite the risk of them coming to harm as their condition worsens.

The new data has renewed fears that vulnerable under-18s are suffering the effects of increasing rationing of psychological help on the NHS, despite high-profile government pledges to improve the service for children.

Family doctors and mental health campaigners voiced concern at the figures, which were obtained by the GP website Pulse. Dr Dominique Thompson, a GP in Bristol who specialises in young people’s mental health, said the figures showed that NHS children and adolescent mental health services (CAMHS) were “failing the next generation. We risk our CAMHS becoming a source of national shame if they continue to be so poorly resourced.”

Sarah Brennan, the chief executive of the charity Young Minds, said the figures revealed a highly damaging postcode lottery in care. She said: “It’s unacceptable that so many vulnerable children aren’t getting the support they need. Without treatment, children are more likely to self-harm or become suicidal, to be violent and aggressive towards those around them, or to drop out of school, which can ruin their prospects for the future. Delays can also have a disastrous effect on families, with parents forced to leave their jobs to look after their children.”

Pulse’s figures, obtained under freedom of information legislation from 15 mental health trusts, showed that 61% of children and young people referred for help from CAMHS in 2015 received no treatment. A third were not even assessed for it. Only 20% of under-18s referred to Norfolk and Suffolk NHS foundation trust ended up undergoing treatment, a sharp fall from the 46% who did so in 2013. At Leeds and York Partnership NHS foundation trust it had fallen from 42% to 26% over the same period.

Some children and young people are being referred on to a school counsellor or charity-run mental health service rather than to the NHS, Pulse said. But such organisations are often not the best ones to use, said Dr Faraz Mughal, the Royal College of GPs’ clinical fellow for children’s mental health. Mughal is also a GP in Solihull.

“Recently all referrals seem to get bounced,” said Dr Karen Cox, a GP in Bristol. “They’ve included children who self-harm, a child who was physically abusing his mother and a child with severe night-terrors after the loss of his father. All three of them were advised to contact local charitable organisations.”

Comparative data from the same 15 trusts for previous years showed that access to CAMHS support was being more and more restricted. In 2013, 44% of referrals ended in treatment, but that had fallen to just 39 by 2015.

A recent review by the government’s children’s commissioner for England, Anne Longfield, found that 28% of children referred to CAMHS services from all sources – including parents, schools, social workers and hospitals – were not given access to an NHS service that could help them. In some places as many as 75% of children did get treatment, but in others it was as few as 18%.

The government has allocated an extra £250m a year for the next five years to boost CAMHS provision, but mental health professionals say a lot of the money is not reaching the frontline to enable them to expand capacity.

Simon Stevens, the chief executive of NHS England, told MPs on the Commons public accounts committee last month that CAMHS was the “most creaking” part of the NHS mental health system. Even if all the £1.25bn helped ensure that 70,000 extra children received help, and pledges made in the recent NHS mental health taskforce report were delivered, many young people would still not get the help they need, Stevens said.

He said: “Even if you look at, say, the very important area of children and young people’s mental health services, even the important extra investment that is going in there may mean that, instead of being able to respond to perhaps one in four children who might be defined as having a mental health need, we can improve that, such that we are supporting one in three. That will be hugely welcome for the 70,000 extra children who are getting those services, but that most clearly is not mission accomplished.”

The Department of Health said: “No child who needs help should be refused it. That is why we have introduced the first ever mental health access and waiting time standards and are putting in a record £1.4bn to transform support for young people.”