Callers trying to contact Centrelink have been met with busy signals more than 42 million times in just 10 months.
The figure - which breaks down to almost 140,000 blocked calls per day - has almost doubled in two years.
And for those who do get through, while the welfare agency's average call wait time is about 15 minutes, some groups of people are kept on hold significantly longer, figures released during a Senate hearing reveal.
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Those trying to reach Centrelink's "participation" line are waiting the longest, for an average of 38 minutes, followed by employment and youth and student services at 30 minutes apiece.
Disabled and sick Australians are kept on hold for about 28 minutes, while older Australians wait 18 minutes and families and parents 16 minutes.
A raft of other lines have a combined average wait time of eight minutes, while the debt recovery line is answered within three minutes and employment compliance lines in under one.
Centrelink is hiring an extra 250 phone operators to chip away at the mountain of missed calls and reduce average call wait times.
But Greens senator Rachel Siewert, who has long been interrogating government officials over the ballooning missed calls, is not convinced the government service provider-run call centres will solve the problem.
"We have a system that is so broken that every year the busy signal wait times just climb and climb ... When is this exponential increase going to stop?" Senator Siewert said.
"I will continue to ask the government about this until it is resolved and busy signals begin to drop."
The 42 million missed calls to Centrelink were logged between July 1 and April 30, which was up from 29 million in 2015-16 and 22 million the year before.
