Sacked Australian Border Force boss Roman Quaedvlieg refused to resign after he was found to have improperly gotten his partner a job.
Mr Quaedvlieg was fired on Thursday for abusing his power by helping his partner get a job at Sydney Airport.
He also made a "false statement" to now-Home Affairs Minister Peter Dutton about his personal relationships, and failed to disclose a significant change in his personal life.
"I had been given a short opportunity to resign prior to termination, however I chose not to do that as it is tantamount to a concession of culpability, which I strenuously deny," Mr Quaedvlieg said in a statement to media outlets.
Governor-General Peter Cosgrove on Thursday sacked Mr Quaedvlieg, on advice from the government, after he modified policies to advantage a candidate for Border Force employment.
"Needless to say it is extremely unfortunate that it was necessary to terminate Mr Quaedvlieg's appointment," Mr Dutton said in a statement.
"He has provided long and conspicuous public service in the critically important areas of law enforcement and national security.
"However the relevant conduct went beyond an isolated error of judgment and ultimately undermined his capacity to continue in the office of ABF Commissioner."
Mr Quaedvlieg had also not disclosed the relationship within a reasonable time and his conduct amounted to "misbehaviour".
The now-sacked boss has been on paid leave since May last year, earning more than $500,000 while off work.
Mr Quaedvlieg reportedly helped his girlfriend, an ABF employee, get work at Sydney Airport, but he denies the "particularised grounds" of the inquiry.
He has previously criticised the length of time it took to investigate the matters, and he says he will pursue his options "more formally in the relevant forums".
His conduct has been the subject of two confidential reports, one from the corruption watchdog and one from the head of the prime minister's department.
"He engaged in acts, and made omissions, which materially advantaged that candidate over other comparable candidates for ABF employment," Mr Dutton's statement said.
Attorney-General Christian Porter said he was called in to make the decision on Mr Quaedvlieg to make sure there could be no allegations of bias against Mr Dutton.
Labor's Shayne Neumann said he was concerned about leaks from the investigation into Mr Quaedvlieg and wants police to look into them.
CPSU National Secretary Nadine Flood said it has been "incredibly frustrating" for Border Force officers watching Mr Quaedvlieg's drawn-out case.
"Staff want to see that the same standards are applied to everyone, including those at the very top," she said in a statement.