A teenager with an eating disorder was told that she "wasn't thin enough" to get mental health support, a new report has revealed.
The Care Quality Commission (CQC) said that too many children and young people find themselves at "crisis point" before accessing mental health services.
The CQC's review of mental health services for children and young people in England found that children face long waiting lists, inappropriately high eligibility criteria and gaps in service provision which make it difficult for them and their families to get support.
The Children's Commissioner for England said that some children had divulged to her that they "felt they had to attempt to take their own life in order to access treatment".
And the charity Young Minds said that it is contacted regularly by young people who have started to self-harm or become suicidal while waiting for treatment.
The comments come after the CQC warned that a lack of support for children with less severe mental health problems could result in their condition deteriorating to the point that they need much more intensive treatment.
The authors of the report highlighted a "vicious cycle" where services struggled to meet demand - meaning children were left languishing on waiting lists or without help, which in turn led to their problems escalating "to the point of crisis".
One young person told CQC: "You shouldn't have to be suicidal to get an appointment".
And while discussing eligibility thresholds for care, a parent who had sought help for their daughter told the watchdog: "At first we were told she wasn't thin enough for eating disorder services. If people were seen earlier it would cost a lot less."
Meanwhile, CQC, which examined the care in 10 areas of England, found that some children are "bounced" between different parts of the system due to confusing referral routes and staffing shortages were leading to delays in children's access to services.
CQC said that health care, education and other public services are not working together as effectively as they could to support children.
It said that proposals to enhance mental healthcare for youngsters were welcome, but added that the pace of delivery must be accelerated to protect children.
The watchdog has also made a series of recommendations for people who work with children, including a specific call on the school inspection service Ofsted to recognise and assess how schools support children and young people's mental health.
CQC's lead for mental health and deputy chief executive of hospitals, Dr Paul Lelliott, said: "Children and young people deserve to have their mental health needs and wellbeing put at the heart of every decision, be that planning, commissioning or resourcing.
"Currently, this is not the reality everywhere and we heard from too many young people who felt they could only access care at a crisis point because local services are not working together, or are not able to work together effectively to support their mental health and wellbeing."
Commenting on the report, Anne Longfield, the Children's Commissioner for England, said: "Too often referrals are only made when a child is at crisis point and sadly some children have even told me that they felt they had to attempt to take their own life in order to access treatment."
Sarah Brennan, chief executive of the charity YoungMinds, added: "Every day we get calls to our Parents Helpline from parents whose children have been waiting up to 18 months for treatment, or who have been told that they don't meet the threshold for services in their area.
"We regularly hear from young people who have started to self-harm or become suicidal while waiting for appropriate help, and who have ended up going to A&E because they haven't been able to find support elsewhere. This simply shouldn't be happening in 21st Century Britain.
"As this report shows, we need to see urgent action across the board."
Claire Murdoch, national mental health director for NHS England, said: "Child and Adolescent Mental Health Services (Camhs) services are now improving, but from a starting point of historic under-funding and legacy under-staffing, relative to rapidly growing need.
"The CQC rightly acknowledge that the NHS's five-year plan for mental health - developed with patients, their families, health professionals and other partners - sets out a clear routemap for improvement and investment, and progress is under way.
"As we look out over the next few years, the CQC is also right to highlight better cross-sector working involving health providers, schools, regulators and Government, as well as children and parents, if we're to put in place care which is timely, supportive and of the highest quality."
To find out more about where to get help visit: www.youngminds.org.uk/find-help/
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