Councils warn they are facing a national special needs emergency and need more funding from government to meet the "colossal demand" for support.
The Local Government Association has urged the government to increase special educational needs and disability funding as new figures show almost 50,000 young people received new EHC plans last year.
Town hall leaders say this means the equivalent of more than 130 extra children and young people with special needs were being supported by councils every day last year.
Figures: Rise in EHC plans
Reporters' take: Why SEND funding is in crisis
Targets: Deadlines missed for 3,800 plans
The chair of the Local Government Association’s children and young people board Councillor Anntoinette Bramble said: “We face a national emergency providing the vital care and support children and young people with SEND so desperately rely on, and the government must address this in the Spending Review.
“The fact more than 130 children and young people are starting support plans with their council every day demonstrates the colossal demand pressures local authorities are under, and the need for this to be properly funded by government."
The LGA's call follows the campaign group SEND National Crisis delivering a petition of more than 12,000 signatures to Downing Street last week, calling for more funding.
Figures from the Department for Education, also published last week, show there has been an 11 per cent rise in the number of pupils with statutory guarantees of support for their SEND in 2019, compared with 2018.
The statistics show a growing demand for EHC plans – with 72,400 requests made for assessments during 2018, a rise of 12 per cent on 2017.
One in four of those who asked for their child to be assessed were refused. And of the 51,600 who were assessed, 48,907 were issued with a new plan during 2018 compared with 42,162 in 2017.
The LGA said this rise in demand coupled with lack of funding has meant that a lower proportion of EHC plans were completed on time.
Sixty per cent of plans were issued within the 20-week limit in 2018, down from 65 per cent the previous year.
Councillor Bramble added: “Preparing EHC plans for children with SEND is a complex and lengthy process, and one that local authorities take extremely seriously and seek to get right.
“While councils endeavour to make sure the increasing numbers of EHC plans are completed on time, this cannot be at the expense of working alongside families and teachers to make sure all children who need support have the most appropriate plans in place.
“Parents rightly expect and aspire to see that their child has the best possible education and support, and councils have done all they can to achieve this. However, funding has not kept up with demand, pushing support for children with SEND to a tipping point.”
The LGA estimates councils in England are facing a SEND funding gap of up to £1.6 billion by 2021.
The association said it has seen rapid rises in demand for support following changes to legislation in 2014 which extended eligibility for support to the 16-25 age group.
In the five-year period since, councils have overseen an increase of nearly 50 per cent in children and young people with EHC plans, or in their previous form, SEN statements, from 237,100 in 2014 to 354,000 in 2019.
Children and Families Minister Nadhim Zahawi said: “Education, Health and Care Plans were introduced to provide personalised and tailored support for those children with more complex needs, but we recognise that the 11 per cent increase in plans last year is a clear challenge for the SEN and disability system.
"We will use this data to follow up with local authorities who are not performing well to support and challenge them to improve.
“My ambition for children with additional needs is that they have the same opportunities to succeed in life as any other child and I am pleased to see that children with new plans are securing more placements in mainstream schools, reinforcing our belief that every school should be a school for a child with SEND, and that all schools should be inclusive.
“Whilst we have increased the total amount allocated to high needs funding to £6.3 billion this year, we recognise the pressures in the system and we are working with the sector ahead of the spending review to find a long term, sustainable solution for high needs funding.”