Anxious parents in Wigan are facing a wait of up to two years to get an autism diagnosis for their children because of a staff backlog.
Leigh MP Jo Platt has also highlighted one case where a mother has been told she will have to wait three years for an assessment to be carried out for the condition.
Her intervention has come following a Parliamentary debate calling for standardised assessment times for childhood autism checks.
MPs have been told that in the worst-affected parts of the country there are delays of 125 weeks, even surpassing the Wigan waiting time.
Ms Platt said she knew of one case where a parent had been told her youngest son would have to wait three years for his assessment.
One of his older siblings, in a similar position, only had to wait less than 12 months.
The MP said: “How is it right for her and her son to go through the agony of not receiving appropriate care due to the assessment process?
“That process has a huge impact on children being able to access the schooling environment and support they need.”
While she praised Wigan Council for the steps it had taken to create a better understanding of autism within local services, she called on the Government to ensure there was greater consistency for diagnosis across the country.
Health Minister Jackie Doyle-Price said the Care Quality Commission and Ofsted were working through a rolling five-year inspection programme to examine how local authorities managed health and care plans.
Council bosses in Wigan have confirmed that the average wait for child autism assessments is between 18 months and two years.
Mike Chew, assistant director for children’s transformation and integration, said: “As a local authority we are fully committed to supporting people of all ages who have autism.
“We are committed to giving people access to the right support in a timely manner and accept that increasing referrals has had an impact on the time it takes to complete an assessment of autism.
“These delays are not acceptable and we have invested in additional resources with our partner organisations to improve the timeliness of this work, and get families an assessment outcome.
“We fully appreciate that this has been frustrating for families but want to offer assurances that we do have a solution and this has been communicated to families that are currently waiting. While this work continues we aim to work closely with any affected families to ensure that the appropriate support is in place whilst their assessment is ongoing.”
The council has an Autism Friends programme which works with families and community groups to improve services for people with the condition of all ages.
This could include virtual tours of local facilities and encouraging shopping centres to have special opening sessions for parents with autistic children or adults with autism.