Senator Abetz, who was responsible for the bureaucracy under former prime minister Tony Abbott, said no "noticeable" impact on the government's service delivery had followed its cuts since in 2013.

After a public service commission report released on Monday showed the government had slashed its headcount to 152,095, the Coalition senator said the changes would save about $1 billion per year and help reduce the budget deficit.

Senator Abetz, who oversaw the loss of about 15,000 Australian Public Service jobs, urged more cuts to agency staff and said the public would welcome the latest drop in APS employment.

"The fact that the reduction was achieved without any noticeable impact on the service delivery of government shows that Labor allowed the APS to get out of control," he said.

"I congratulate the government on again reducing the size of government and hope that there is a continued focus and emphasis on a further reduction of public service numbers by way of natural attrition."

While he no longer holds any government roles, he remains a powerful influence among conservative Liberal parliamentarians and his views regularly mirror those of ousted leader Mr Abbott.

Crawford School of Public Policy director Helen Sullivan said the size of the public service was less relevant than its ability to carry out its role.

Senator Abetz's comments were sweeping statements made without referring to clear evidence, she said.

"You can have a big public service that's not very adept or a small public service that's agile, or a large public service that's agile.

"It really depends on what you want the public service to do, and I think that's the fundamental question they're not asking," she said, referring to the Coalition government.

Cuts impacted the public service's ability to prepare for and respond to changes including technological disruption, she said.

Senator Abetz's claim job cuts had not hurt government services has drawn fire from the main public sector union and Labor, who pointed to Centrelink call wait time blow-outs, IT disasters and other departmental crises as the result of falling APS staff numbers.

The Community and Public Sector Union said Senator Abetz was being dishonest, adding that the Coalition was wasting billions of dollars on contractors and labour hire to pretend it could keep cutting the public service.

CPSU national secretary Nadine Flood described the cuts as an ideologically-driven waste of money.

"Try telling someone who's tried to get through to Medicare or Centrelink on the telephone or has been caught up in the robo-debt debacle that there's been no noticeable impact from the Abbott-Turnbull government's cuts?" she said.

"This government pretends it has cut more but then turns to a private company through labour hire or contracting arrangements to do that work at a higher cost under terrible pay and working conditions.

"Not only do they pay more for less but it means there's none of the transparency or accountability that's essential to good value, quality services."

Fenner Labor MP and shadow assistant treasurer Andrew Leigh said the government had treated public servants abysmally, referring to job cuts and the rise in contractors.

"No wonder the tax office website keeps crashing, 55 million Centrelink calls went unanswered and the rollout of the Health Care Homes initiative has been botched."

Workplace union Professionals Australia's ACT director David Smith said more public service job cuts would hurt regional Australia in addition to Canberra.

"Yet at the same time as the government has continued to cut jobs, the cost of the public sector continues to go up because of an over-reliance on consultants, contractors and labour hire," he said.

"In Defence alone this has ballooned to being larger than the ongoing APS workforce."

Despite implementing a "recruitment freeze" after the Coalition won the 2013 election, the government was unable to shed public service staff by natural attrition alone and the number of redundancies during that period was about triple the usual rate.