Samantha and Jonathan Lethbridge say their daughter has had episodes of suicidal thoughts 40 times in the past two weeks.
They have been forced to care for her at home since an initial episode in A&E;, when they were told she would not be able to get psychiatric care.
“Our daughter needs urgent medical support and there is nothing available,” said Mr Lethbridge.
“This is far worse. Her life is at risk. And we are being told there is nothing they can do for months.”
David Law, chief executive of the Hertfordshire NHS Community Trust, said: “It’s a very disturbing story, and it highlights some of the really big issues that we have around child and adolescent mental health in this country.”
Campaigners say that many families across England are being driven to desperate measures to provide care for their mentally ill children.
Nick Harrop, from charity Young Minds, said: “Far too often children and young people have to wait for months to get appropriate treatment, if they get treatment at all.
“When a child needs inpatient care, when their crisis is so severe, there should be a bed available. But all too often there aren’t enough beds available.
“It’s an incredibly traumatic time for young people and their families and they need to get comprehensive support,” Mr Harrop added.
The NHS said it acknowledges the problem but is investing heavily in improving services.
A spokesman said: “It is clearly the case that CAMHS services need to expand and over the next five years Government has allocated a cumulative £1.4bn to children and young people’s mental health services plus some new waiting times to ensure patients get better care more quickly.
“Last week, the NHS set out detailed plans to expand mental health services and staff so as to eliminate distant out of area placements and help ensure patients get better care more quickly.
But the Lethbridge family said they feared it may be too little, too late.
“For us it’s almost too late,” Mr Lethbridge said.
“We are at the worst possible point we could be with our daughter.
“But we hope that for other children, the next child that comes in that’s similar for our own daughter, that things might change for her.”