According to the report, more than 3000 incidents were logged within its first eight months of operation, which staff said ran slower than the older system and required them to swap between two systems.

The number may not represent the full picture, as staff also said they didn't always log issues with the system if they were encountered while on the phone to a client, in order to minimise the amount of time a caller spent waiting on the phone to the department.

Human Services first had issues with the Pluto software system not long after it was implemented in 2017, creating the need for staff to both work in the new system and its predecessor Cuba at the same time.

The Deloitte report, which was delivered to the department in April 2018 and cost $1.09 million, was released to a Senate estimates committee on election day, after Labor senator Murray Watt requested that it be tabled.

When the program was first implemented, departmental officials denied it wasn't working, or was slower than the system it was supposed to replace.

The report also confirmed call wait times has increased after the new software was introduced, due to the slower running time of the new program and the need for staff to move between the new system and the old one.

"Since the implementation of the Pluto solution there has been an increase in the average handle time of over 2 minutes across the business and over 3 minutes in the Mainstream Services division," the report said.

"This has contributed to increases (over 25 per cent) in both work on hand and work overdue despite a ~12 per cent reduction in total inbound calls. The increase in call handling times has also resulted in more staff taking inbound calls rather than actively following up issues with customers through outbound calls, noting a 30 per cent reduction in successful outbound calls and the impact that this has on the work on hand, which in many cases cannot be completed without contacting the other party to a case."

The department spent its $102.3 million budget on the project in its first two years, as well as an extra $33 million. Departmental secretary Renee Leon told Senate estimates the software is now paid for out of the area's "business as usual" IT budget and that any further changes to fully replace the old system have not been decided on.

Ms Leon said the new system was used for clients accessing the system online, and for new clients, but staff would continue to use Cuba for existing clients.

"The Cuba IT system is still in use and we have deferred decisions about its replacement for the time being," Ms Leon said at Senate estimates in April.

"At the moment there is no pressing need to take fresh decisions about the Cuba system."

The Deloitte report said there was "still a strong burning platform for further investment" but that it wasn't as simple as replacing the old It system, rather "a broader transformation of how services are delivered".