Reports reveal that the NDIS received nearly 1500 reports of serious incidents against its participants, including 60 sexual abuse allegations.
Concerns have been raised that a reported 1500 serious incidents against participants in the National Disability Insurance Scheme, across six months - including instances of sexual abuse - could be a conservative estimate.
Greens senator Jordon Steele-John says the figures quoted by the ABC for the second half of 2018 are probably "just the tip of the iceberg".
"There are so many people who, because of their disability or circumstances, physically cannot use the safeguard system to report their experiences," he told AAP in a statement.
"Individuals with mobility issues, who are hearing impaired or who require support and assistance may not physically be able to use a telephone, or may be in a situation where they actually rely on their abuser to complete these tasks."
Labor's social services spokeswoman Linda Burney also believes the number of serious incidents against people with a disability would be much higher than the number reported.
"People with disability deserve quality support and services, but the government has deliberately starved the NDIS to prop up the budget," she said.
Between July and December 2018 the disability watchdog was told of more than 60 instances of sexual abuse, as well as 227 allegations of unlawful physical or sexual contact, the ABC reported on Wednesday.
Of the total reports, almost 500 incidents were related to abuse and neglect of NDIS participants, and 250 allegations of serious injury.
Prime Minister Scott Morrison last week launched a royal commission into the abuse and neglect of disabled Australians, which will run for three years and report in April 2022.
Senator Steele-John says it's urgent for the royal commission to get under way.
"To provide disabled people with assurances that the violence, abuse, exploitation and neglect we face is being taken seriously," he said.