Children with special educational needs and disabilities (SEND) are being failed by a system “on the verge of crisis” as demand for specialist support soars and threatens to bankrupt local authorities, a Guardian investigation has revealed.

Parents of children with SEND are increasingly locked in prolonged and costly disputes with councils across England who are too often failing to deliver on their legal obligations.

As a result, many of the most vulnerable children in society end up without the support to which they are entitled, and are out of school for months – even years – as parents battle to secure the right provision to meet their child’s needs.