The Public Service Commissioner, who will resign on August 8, spoke out this week after Labor senator Jenny McAllister questioned his impartiality and accused him of undermining staff.

In an article in The Canberrra Times, the senator said Mr Lloyd's replacement must be a leader whom public servants respected.

The commissioner said the senator's comments were inaccurate and insulting.

"I have tolerated numerous personal attacks and smears during my career. Most have been levelled by union officials and the labour movement. I have been restrained in my response," he said.

"Public servants must avoid becoming participants in political debate. However, I am firmly of the view that [Australian Public Service] employees are within their rights to comment on, and respond to, unjustified personal smears."

He took umbrage at the description of him as "someone from outside the APS", saying it "ignores the fact that most of my career has been in the APS, 31 years in fact".

"In addition, I served 11 years in senior positions in the Victorian and West Australian public services. The assertion that my appointment 'marked a break from our public service traditions' is a fallacy."

Mr Lloyd has worked for the right-wing Institute of Public Affairs and was John Howard's choice to head the building industry watchdog, seen widely as a crackdown on construction unions.

The Labor Party and unions criticised the Abbott government's decision to name him as Public Service Commissioner in 2014.

Mr Lloyd announced his resignation in June amid reports he is under investigation for alleged misconduct, though he says he told the government of his intent to leave before he was aware of the complaint.

Senator McAllister said this week the commissioner was "never able to put partisan leaning completely aside", oversaw "a draconian social-media policy" and "spent years trying to stymie public servants' pay rises and cut their conditions".

But Mr Lloyd said he was proud of his achievements. He said the senator "attributes me more influence than I actually dispense".

He named among his achievements modernising the APS employment framework, reforming recruitment practices, and introducing a talent identification and management program.

"The public sector unions, in a desperate plan to arrest declining membership, adopted a negative approach to bargaining. The most pernicious outcome of the union strategy was to delay the receipt of pay increases by their members."

"Restrictions on the engagement of staff and their deployment have been modified. Changes have been introduced to relax workplace rigidities and empower a modern and effective employer-employee relationship in most workplaces," he said.

"APS agencies have continued to look for more effective ways of engaging with citizens through digital platforms and by more creatively using our data holdings. I am continually reassured by the way the APS is willing to review its performance, be held accountable for its work and step up to embrace new challenges."

He said the independent review of the APS, due to report early next year, would ensure the public service remained professional and efficient.