More than 2,600 intellectually disabled people have no services or have not received a diagnosis of their condition from health authorities, new figures show.
The Intellectual Disability Database for 2001 shows that, despite "significant" investment in the area in recent years, there has been little progress in cutting waiting lists to residential and day services.
It says most of the people without services need either residential placements or a daycare programme "immediately".
This includes a group of 410 intellectually disabled who are forced to reside in psychiatric hospitals and have been identified as in need of being transferred to more appropriate accommodation.
The report says a further 10,182 people who are currently receiving services require alternative, additional or enhanced services within the next five years.
It also underlines the need to maintain investment and plan for the future to avoid a "crisis" for families and service providers.
The authors of the report suggest that the reasons why there are long waiting lists, despite significant investment, is due to improved life expectancy among adults with intellectual disability.
It also says pressures on the system will increase even further in the years ahead due to the increasing age profile of the intellectually disabled and the baby boom of more than 30 years ago.
"Taken together, the combined effects of the baby boom generation and increased longevity, will result in significant demand for additional resources and will present major challenges to service planners and providers - this baby boom generation, born in the 1960s and 1970s will begin to reach age 55 in 2015, just 12 years away," the report says. Ms Deirdre Carroll, of NAMHI, an umbrella group representing the intellectually disabled, said she was not surprised by the figures and said more investment was needed in the area.
"The important thing to remember is that there are people behind those statistics. We're hearing the awful day-to-day stories of elderly people coping with children who have challenging behaviour, or intellectually disabled ending up in psychiatric hospitals. This is all happening."
In a foreword to the report, the chairman of the National Intellectual Disability Database Committee, Mr Brendan Ingoldsby, said the data for 2001 represented the first full year of a three-year programme of investment by the Government.
He said this was not fully represented in the report as the figures were based on data collected in the first half of that year.