, children who have the condition are eight times more likely to be permanently excluded than their peers, and four in 10 children with autism have been informally excluded during their time at school.
Another survey, from the National Autistic Society (NAS) in 2012, found that 34 per cent of people had to wait three years for a diagnosis, with a further 30 per cent waiting between one and two years (bit.lyAutismReport).
"Such delays often mean that children miss out on support or are given the wrong help, which can have a highly damaging impact on their education, mental health and long-term development," said Dan Leighton, policy and parliamentary officer at the NAS.
Jo Galloway, principal of the NAS' Radlett Lodge School, said children who had to wait for a diagnosis could be "traumatised" by their experience in mainstream schools and develop poor behaviour and low self-esteem as a result.
Dr Crane's study finds that most parents identify problems before their children reach the age of 5, but they often wait a year before seeking medical help. After contacting a doctor, parents wait an average of 3.6 years to receive a diagnosis; when children are suffering from Asperger's this rises to more than four years. Post-diagnosis, 35 per cent of parents receive no offers of help or assistance, the survey results show.
"Further research is needed to gain a better understanding of how services that assess children with suspected [autistic spectrum disorder] in a prompt and timely manner are structured and organised," Dr Crane writes.
Autism is believed to affect about 1 per cent of the population, so "diagnosing the condition represents a significant public health issue", she adds.
`Low self-esteem becomes entrenched'
Jo Galloway, principal of the National Autistic Society's Radlett Lodge School, says: "In my experience, when a child is diagnosed early, the right intervention can be put in place and children can be supported to progress and live the life that they and their parents choose.
"But in reality, too many parents experience long delays getting a diagnosis for their child and have to wait far too long to access the right support, which in most cases slows down or limits progress.
"For example, a number of young people have joined our school at the age of 13, 14, 15 or even older, having never been in specialist education before. In the absence of appropriate support at a young age, some of them had developed inappropriate behaviours and low self-esteem, which had become entrenched.
"Others were traumatised by negative experiences at former schools, which too often included multiple exclusions - something that, in our experience, is generally avoidable when the right support is in place."
When cuts bite
As reported in TES last month (23 January), the government has cut spending on Child and Adolescent Mental Health Services (CAMHS), from pound;766 million in 2009-10 to pound;717 million in 2012-13, the most recent year for which figures are available.
A survey of headteachers conducted by the CentreForum thinktank recently found that more than half do not believe CAMHS is working properly.