The opposition leader, Peter Dutton, has accused Labor of “political interference” in “seeking retribution” against Michael Pezzullo after he was stripped of his Order of Australia appointment by the independent body that runs the honours.

Pezzullo, a former top bureaucrat, was sacked as the home affairs department secretary in November 2023 after an independent inquiry found he had breached the government’s code of conduct at least 14 times, including using his power for personal benefit.

The inquiry had probed a series of text messages he sent to a Liberal party insider in an alleged attempt to influence political processes.

It was revealed on Friday that Pezzullo’s appointment as an officer to the Order of Australia was terminated in September 2024, according to a document made public.

While Pezzullo dismissed the news in a statement as not amounting to “a hill of beans in this crazy world”, opposition frontbenchers have queried the reasons behind the decision.

On Thursday, Dutton claimed without evidence that the decision showed a “clear demonstration of political interference”.

“Well, it’s vindictiveness in its worst form. I do think it’s bizarre,” Dutton told 2GB Radio.

“This is a clear demonstration of political interference in the process … there’s no impropriety alleged against him that would warrant the stripping of this honour, and it is nothing more than the government trying to seek retribution against him.”

The opposition leader said the finance minister, Katy Gallagher, should disclose any instructions given to the Council for the Order of Australia “because it’s not a fair process. In the end … it should be impartial and independent – and it’s been anything but”.

Gallagher told Sky News on Sunday the decision was a matter for the council and she played no role in it.

“[Pezzullo] was a long-term, career public servant in Canberra. He did many good things, but this is a matter for the council. They’ve had a look at it, they’ve considered it against their criteria and they made a recommendation to the governor general,” she said.

Pezzullo was appointed as an officer of the Order of Australia in June 2020 as part of the Queen’s birthday honours for “distinguished service to public administration through leadership roles in the areas of national security, border control and immigration”.

Under the rules, the council can strip a recipient of the honour if they have “behaved or acted in a manner that has brought disrepute on the order”.

The inquiry into Pezzullo, conducted by the former senior bureaucrat Lynelle Briggs, found he had breached the rules at least 14 times relating to five “overarching allegations”.

Those included using his power, status or authority to “seek to gain a benefit or advantage for himself”, failing to act apolitically, failing to disclose a conflict of interest and failing to maintain confidentiality of sensitive government information.

It also found Pezzullo engaged in “gossip and disrespectful critique” of ministers and public servants.

Speaking to the ABC’s 7.30 program in April this year, Pezzullo said he should not have been sacked but “perhaps an appropriate censure or reprimand would have been relevant”.

“It was considered, in terms of the finding, that I was using channels outside of the established mechanisms to pursue those ends. I accept that. I made a mistake,” he said.