The HSE received 6,755 new assessment of need (AON) applications for children last year, the highest number since the legislation began almost 20 years ago.
By the end of 2022, there were still 4,613 applications overdue for completion. On top of that, a High Court ruling last March which found that the HSE's Preliminary Team Assessment (PTA) method of dealing with AON applications was unlawful meant another 4,698 children whose application underwent the PTA process required further diagnostic assessment.
The HSE said: "It is anticipated that a further cohort of families may request additional assessments."
It has led to what one child law solicitor described as "gridlock" and prompted the Psychological Society of Ireland to query whether the HSE has an adequate plan to tackle the issue.
Families can apply for an AON if their child has a disability or they suspect they may have a disability. It is designed to identify the child's health needs and the services they require. An assessment officer must arrange the referral within three months of receiving a completed application, triggering a further three-month period in which to assess the child and complete the Assessment Report.
However, many cases were delayed beyond that statutory timeframe, with the HSE then introducing a much-criticised Preliminary Team Assessment to speed up how cases were dealt with. Last March, the High Court ruled that this process was outside the law. The HSE did not appeal the ruling.
A HSE spokesperson said: "Since a High Court judgment in March 2022, the Preliminary Team Assessments (PTA) approach, as defined in the HSE’s former Standard Operating Procedure for Assessment of Need, is no longer utilised to fulfil our obligations under the Disability Act 2005.
"This has resulted in a growth in the numbers of overdue Assessments of Need. The HSE continues to make every effort to comply with its legislative obligations under Part 2 of the Disability Act (2005) and additional funding has been secured to support the additional assessments required."
It said an 'interim clinical guidance' has been developed to replace the PTA, has been clinically approved, and will be implemented following discussions with staff representative bodies.
Some 3,071 AON assessments were completed last year but there were 4,613 applications overdue for completion at the end of December, just 90 of which were delayed due to exceptional circumstances.
Of the overdue assessments of need, 3,155 were overdue by at least three months. The areas with the biggest backlogs are Dublin North City and County (CHO9), Dublin South and West, Kildare and West Wicklow (CHO7), and Cork and Kerry (CHO4).
The HSE also said that the average duration of the assessment process, per report completed during 2022, was now 16.5 months.
Solicitor Gareth Noble of KOD Lyons, who has been involved in a number of legal actions relating to the AON process, said the HSE had been "the author of their own misfortune".
"The whole system is now gridlocked out of their insistence with persisting with a model everyone warned them was not compliant with the Disability Act," he said.
"This issue did not arise out of litigation, the litigation arose out of longstanding delays in the assessment process."