Child Support Agency staff report the new system, called Pluto, is slower and clumsier than the obsolete technology it was supposed to replace.

Both frontline public servants and the main workplace union has told Fairfax Media that large numbers of CSA public servants being ordered to drop everything to help with "emergency escalations" as the agency's phone lines are swamped with irate clients.

But the Department of Human Services, which runs the Child Support Agency says the roll-out of the new system is going smoothly and has denied that any "emergency escalations" have occurred during the "implementation" period.

Payments to the hundreds of thousands of families who depend on the system have not been affected, it is understood.

The Child Support Agency's main workplace union, the CPSU, says aggression from customers is up, staff morale is down as a result of the new system and will hold talks with senior officials from Human Services on Wednesday to discuss their concerns.

The system that is supposed to administer the payments that support more than 1.2 million children, has had a long and troubled history even before it was rushed into service in April.

Pluto is the fourth technological fix to be tried since the then- Labor government announced in 2013 its intentions to replace Cuba, which dates back to 2002 and was hopelessly obsolete four years ago.

Human Services has consistently refused to reveal how much taxpayers' money it has sunk into the project but Fairfax understands the original $109 million budget has been exceeded by a large margin.

Now that Pluto is finally operational, one frustrated user told Fairfax the process was a "shambles"

"It's no easier and considerably slower than Cuba while we're left making excuses to customers to calm them down," the insider said.

"We only have about half the information we used to, so it's very difficult telling customers where their payments are, when they can expect to receive payment."

A union bulletin to its members at the CSA said 'all hands on deck' emergency escalations to phones have become a daily event as the slower system is impacted on call wait times, that the escalations were lasting for days and creating huge backlogs of work.

But Human Service spokesman Hank Jongen gave an upbeat assessment of Pluto's performance.

"There have been no emergency escalations during the implementation phase," Mr Jongen said.

"The department has not observed any systemic difficulties or resulting dissatisfaction from parents during the rollout of the new system.

"Any issues that might arise will be immediately addressed."

"The department has received positive feedback from staff working with the new child support system."

CPSU Deputy National President Lisa Newman offered a conflicting view.

"Our members report poor system performance and a lack of training," she said.

"They also have significant concerns that Cuba is continuing to underpin the new system, which poses a real risk of an outage or other major failure."