Age Discrimination Commissioner Kay Patterson has questioned the age cut-off for the National Disability Insurance Scheme, declaring it as "odd".
Only people aged between seven and 65 are eligible for the scheme.
Speaking at the National Press Club in Canberra on Wednesday, Dr Patterson said the issue needed to be resolved with Australia's population set to become the oldest in its history.
"It seems odd to me that one day before you turn 65 and develop a disability you get the NDIS, and two days after you wouldn't," she said.
"I think it needs resolving."
When the scheme was launched a decade ago the age limit was recommended to avoid duplication of services in the aged care system.
Dr Patterson is stepping down after seven years in the role.
Meanwhile, amid debate over how to cover the rising cost of the scheme, NDIS Minister Bill Shorten dismissed introducing co-payments or means testing.
Kismet, an online platform business that links people with a disability to NDIS providers, has suggested implementing co-contributions in a similar vein to the childcare system.
The NDIS is expected to blow out to about $60 billion a year by the end of the decade, sparking calls to make it more sustainable to ensure longer-term viability.
Asked if co-payments or means testing would be considered, Mr Shorten said: "No."
"To be honest, I'm not going to pretend I'm going to give it too much oxygen," he told ABC Radio on Wednesday.
Mr Shorten said the NDIS needed longer-term planning and that there was too much focus on annual plans.
However, he said co-payments were not the way to go about reform.
"When a service provider says 'I just want different people to pay me more money', I'm not immediately swayed by that logic," he later told reporters in Canberra.
"This scheme needs reform, but it's here to stay. We want to make sure every dollar gets to the people for whom the scheme was designed."
Opposition NDIS spokesman Michael Sukkar said Labor had no plan to achieve savings and no participant was safe.
"The government is getting increasingly desperate to now deliver the savings they promised," he said.
"They've already threatened the removal of children with an autism diagnosis from the NDIS, and now we see Bill Shorten threaten participant plans through stricter evaluation processes."
Mr Shorten also said he did not accept there were tens of thousands of people on the scheme who should not be.
