A key concern of parents has been the deliberate withholding of legally-binding support plans by councils so they can avoid having to commit resources to vulnerable pupils.

While not all children with additional support needs (ASN) require a co-ordinated support plan (CSP) it has an important status because it is a legal document requiring councils to ensure pupils receive appropriate support.

In particular, the documents are vital for pupils with more severe issue who require support from a number of different services such as education, social work or health.

Before the Additional Support for Learning Act in 2004, about two per cent of pupils in Scotland had a statutory support plan and, when the CSP was introduced, the Scottish Government promised there would be no decline in the proportion of children receiving them.

However, since 2011 there has been a year-on-year reduction in the number of CSPs opened, with the most recent figures showing a drop from 3,448 to just 1,986 last year.

Worryingly, previous research has shown pupils from less advantaged backgrounds are more likely to be identified as having ASN, but are less likely to have a CSP because middle class parents are more likely to have the resources and resilience to pursue one even when councils are resistant.

Professor Sheila Riddell, chair of inclusion at Edinburgh University, said if the trend continued support plans could virtually disappear.

She said: "Councils are largely unconcerned about the decline in the use of CSPs, regarding them as cumbersome and time consuming.

"Local authorities argue they prefer to use other types of plan despite the fact these are not specifically education documents and have no directly enforceable rights associated with them.

"Parents, on the other hand, believe statutory plans are important to ensure children’s needs are properly assessed, recorded and reviewed."

Mrs Riddell said there were "mixed messages" from the Scottish Government on the importance of CSPs.

She added: "At a time when budgets are being squeezed, a number of changes are needed. The qualification criteria for a CSP should be simplified, so that a child should be entitled to a statutory support plan if they require support not normally available in school.

"Secondly, there should be training for local authority and school staff so there is better understanding of the system in general, including statutory entitlements."