Nearly 200 children a day are being placed on plans to protect them from neglect and abuse, research has found.
Children's services are being "pushed to the brink" by the demands of dealing with the equivalent of six classrooms' worth of pupils every day who are at risk of significant harm, the Local Government Association (LGA) said.
It warned the pressure on departments across England is "no longer sustainable".
Councillor Roy Perry, vice chairman of the LGA's children and young people board, said: "It is absolutely vital that councils are able to support families and help children who are at risk of significant harm.
"But as these figures show, the pressures on councils are mounting as a result of a huge increase in demand, with the number of children being placed on child protection plans the equivalent of six classrooms' worth of pupils every day."
Councils put child protection plans, which are coordinated by a social worker, in place to support families when children are believed to be at risk of harm, such as neglect and physical, sexual or emotional abuse.
Some 182 children a day are on the schemes, double the amount a decade ago, according to LGA analysis of official figures.
Around 66,410 plans were started by councils in England during 2016/17, compared to 33,300 in 2006/7.
Mr Perry said: "Last week's care crisis review highlighted the significant pressure on the care system, with the number of applications to take children into care more than doubling over a decade.
"But these new figures demonstrate that the pressure on children's services goes much deeper, with high risk cases being managed outside of the care system also increasing at an alarming rate.
"This is no longer sustainable, with many areas struggling to cope. Children's services are being pushed to the brink, and face a funding gap of almost £2 billion by 2020 just to maintain current service levels.
"We really need the Government to commit to fully funding these services so that councils can manage the rising demand for help, while also providing the additional resources they need to support families before problems escalate to the point where a child might need to come into care."
Shadow children's minister Emma Lewell-Buck said: "This is yet another damning set of statistics that shows the Government's approach to vulnerable children is failing.
"As Tory austerity and cuts to early intervention continue it should come as no surprise that referral rates are skyrocketing. Starving local authorities of money and ignoring their warnings will only result in more children and families being failed.
"Thanks to Government inertia we have now passed crisis levels. The Government must act now.
"The next Labour government will give our councils the funding needed to protect these vital services, ensuring that every child gets the support they need in a country for the many, not the few."
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