Centrelink is pressuring its public servants to manipulate waiting time figures and make the agency's performance look better, insiders have alleged.

Workers at Medicare and Centrelink have given disturbing accounts to their union of life on the front lines of the agencies which have been subjected to successive rounds of cuts over recent years.

One public servant said Centrelink was "pretending" it could do more with less resources and it was "fraud on the people of Australia".

But Centrelink's parent-department, the giant Human Services, rejected the allegation on Thursday that wait time figures were manipulated.

The Community and Public Sector union also says its members told of inadequate staffing levels, massive processing delays, customers not receiving payments because of mistakes by over-worked or under-trained workers and staff being encouraged to fudge performance statistics to hide the true extent of problems.

The union says the survey of 800 officials at the Department of Human Services reveals a system close to breaking point.

Union members who responded to the survey, on the condition of anonymity, alleged that various methods were being used to make Centrelink's performance look better than it really was.

"DHS manipulate call wait times by using IIE [casual] staff to answer calls and immediately transfer them to another queue," one public servants said.

"Similarly, customers at centres are being advised to call in.

"It's very deceptive. Yes the queues look shorter, but that's because most people are now being shunted to online services for phone queues."

Another official said their team leaders were being encouraged to manipulate wait time data.

"Customer wait time has blown out again, however the management information used to determine this isn't always accurate," the public servants said.

"The data is highly flawed as it requires manual input from users, and TL [team leader] is quite often encouraged to manipulate wait time figures so things don't look as bad as what they actually are."

Another respondent spoke of the deteriorating customer service standards.

"We used to answer 75 per cent of calls within 150 seconds and now it's lucky to be 1000 seconds and that is a fudged amount," they said.

CPSU National Secretary Nadine Flood said the survey painted a frightening picture.

"But unfortunately an all-too-familiar picture of the critical services provided by Medicare, Centrelink and Child Support. Customers and workers are being pushed to the brink by understaffing; delays mean people are being evicted, forced to abandon their study plans or worse," the union leader said.

"Thousands of DHS jobs have been slashed in recent years and thousands more experienced staff have been replaced with casuals.

"These casual staff want to offer the best service they can to the Australian people and are frustrated that they can't access the training and support they need to help customers.

"The anecdotal evidence of performance statistics being fudged suggests even a figure that damning may be under-stating the true scale of this problem."

A DHS spokeswoman said on Friday that she and her colleagues were "concerned" by some of the material in the survey.

"We are concerned by some of these claims. In particular, we reject the suggestion that our staff manipulate wait time figures.

"Our staff also know that people in hardship should be given priority treatment.

"Around 90 per cent of our workforce is permanent, complemented by staff on temporary employment.

"This staffing profile and mix is not unusual for a large organisation."