County councils across England are warning that the cost of covering special needs education is breaking their budgets, with local authorities overspending by more than £100m last year to meet the sharp rise in demand.

Research by the County Councils Network found that some councils had recorded a 90% increase in young people being given care plans requiring special support, with 27 county councils overspending by a total of £123m in 2018-19 at a time when local authority purses are under severe pressure.

MPs on the education select committee have published a report on school funding in England that calls for £1.2bn to fill the deficit in provision for special educational needs and disabilities (Send).

The county councils said the number of young people on education, health and care plans (EHCPs) requiring additional support in their areas had risen by 50,000 in five years following reforms introduced by the 2014 Children and Families Act.

Carl Les, Conservative leader of North Yorkshire county council and the network’s spokesman on children’s services, said the 2014 reforms – which raised the age limit for statutory support to 25 – had been “well intentioned” but were causing severe difficulties.

“Additional demand … has created a financial crisis for some local authorities, with huge rises seeing costs spiral out of control,” he said. “Counties already face a funding gap of £21.5bn over the next five years, and if we continue to overspend at the level we have done it will break many of our budgets.”

Les added that the cost burden was falling on other service areas, with local authorities shifting funds from “mainstream pupils” and reducing preventive services – an approach that would “only store up problems for the future”.

Councils would be forced to make further compromises on their quality of service, he added. “This is why we are urging the new government to urgently inject funding into special education.”

With the number of children and young people on EHCPs rising from 240,000 in 2015 to 354,000 this year, the impact on county councils has been repeated across England.

The network’s call was echoed by the Commons education select committee, whose report on school funding calls for a 10-year settlement along the lines of that agreed for the NHS last year.

It recommends an immediate increase of £760 per student in further education colleges to “urgently address underfunding” in the sector, with FE and sixth-form colleges among the hardest hit by funding contractions, and a “multibillion-pound investment” in schools.

Robert Halfon, the Conservative MP who chairs the education committee, said he wanted “a proper 10-year plan and long-term funding settlement” for school budgets.

“There is a crisis of confidence in the ability of mainstream schools to provide adequate Send support. This needs to be tackled through increased school funding to support better early intervention,” he said.

Jules White, a secondary school headteacher who helped found the Worth Less? group to lobby for better funding, welcomed the call for an increase in per-pupil funding and said there was an urgent need for more support for special needs education.

He said: “It’s a devastating report and the Department for Education and wider government should be ashamed that they have failed to publicly recognise and then adequately address a funding crisis that’s having severe ramifications for the most disadvantaged children and all schools across the country.”