An NDIS inquiry has heard outsourcing is hobbling the agency’s work.

A joint parliamentary inquiry into the shortcomings of NDIS planning processes has been swamped with stories of potential participants waiting months for their plan to be finalised.

Many wait over two weeks just for an email to be returned.

The Community and Public Sector Union says scrapping the average staffing level cap is the only way to address the issues.

The NDIS has a staffing ceiling of the ceiling 3500, with about 7000 people working for the agency through labour hire firms of local area coordinators.

“Our members are telling us the staffing cap is having a huge impact on their ability to give quality service, with great swathes of the scheme outsourced,” Community and Public Sector Union deputy secretary Beth Vincent-Pietsch has told the Canberra Times.

Labour hire staff are on rolling contracts with little job security, leading to high staff turnover.

This means NDIS participants have a lack of continuity, often having to tell their story over and over again to different staff.

Additionally, labour hire staff cannot approve plans, so they all have to be audited by ongoing staff.

Call centre staff often lack access to the information participants request, so they often have to do callbacks.

All of this is occurring while a backlog of more than 10,000 reviews continues to grow.

The union says staff report high levels of anxiety before calling participants, as they have often been waiting months for their cases to be examined.

The NDIA spent $430 million on labour hire in the last finical year.

“Imagine if they scrapped the cap and invested that in ongoing employees,” Ms Vincent-Pietsch said.

“Lots of labour hire staff are great staff but they won't stay unless there's longer term job security. It's not like they can say they don't have the money. It's frittering through their hands as it's being given to labour hire companies.”

The Productivity Commission has previously argued for the cap to be axed entirely, saying it makes it difficult to build institutional expertise and capability.