Figures outlined in the Assembly this week reported that 900 children have not been seen by health experts within the recommended 13 weeks. Almost half of these (476) have been waiting longer than 26 weeks with 78 forced to wait more than a year.
Member of the Legislative Assembly Dominic Bradley said: "These are children, who if they are found to have [an] ASD will not have got the support that they require in school and outside of school during the time they have spent waiting for a diagnosis to be complete.
"It is very clear that the prevalence of autism is increasing in our society but that is not being accompanied by the necessary increase in support and services and by the necessary decrease in waiting times for diagnosis and for early intervention."
The findings are the result of a publication from the Department of Health, Social Services and Public Safety entitled ‘Autism Spectrum Disorder Statistics for Northern Ireland’.
In it, MLAs were also told autism rates had increased by 67% over the past five years, with one in 54 school pupils being diagnosed with an ASD.
Mark McConville from CAPA (Children, Adults, Parents and Autism) said that families were being let down by the Executive due to the long waiting lists.
"I think the main difficulty initially is getting the diagnosis," he said. "This can be very, very stressful for families, who know there clearly is a challenge and an issue with their children, but they can't actually seem to get through to their healthcare professional.
"As far as I can see, it's hard to see that the Executive is actually helping our children and in fact in many cases, they might be failing them."
Read the report in full at www.autismni.org