Michael Pezzullo agreed to stand aside from the prominent public service job after a plethora of leaked text messages revealed he used a political back channel to try and influence two former Liberal prime ministers.

One batch of leaked texts showed him suggesting ministerial appointments and sackings to Liberal powerbroker Scott Briggs.

Mr Pezzullo agreed to stand aside after Home Affairs Minister Clare O’Neil asked him to on Monday, pending a review by the public service commission.

It is not suggested the messages show corrupt or illegal conduct but that Mr Pezzullo arguably overstepped the required impartial nature of heading a government department.

Opposition foreign affairs spokesman Simon Birmingham said it was unlikely Mr Pezzullo would return to the position.

“He deserves the right to have a proper process, but clearly, I think, the odds are stacked against in terms of the concerns that are being weighed,” he told Sky News on Tuesday.

“I respect that process and let’s see how that runs through, he’s obviously stood aside while that is considered.”

Nationals Senator Bridget McKenzie said the boundaries between politics and public service were important, but praised the previous work of Mr Pezzullo.

“He’s a patriot and I know that everything that he does, no matter who he’s working for – whether he’s working for the former leader of the Labor Party Kim Beazley or the now current minister – is focused on our national security,” she told ABC TV.

However, she said Mr Pezzullo needed to address critical questions in the inquiry about the text messages, including those commenting on former Liberal ministers Julie Bishop and Marise Payne.

MEAA Media Federal President Karen Percy said the reports on Mr Pezzullo pushing for the government to criminalise reporting on some whistleblower-sourced stories were “particularly alarming”.

“D-notices have been used during wartime on rare occasions for the protection of national security … but Australia is not at war and there is no justification for their use now,” she said in a statement.

“This is just one example of a very disturbing problem that goes beyond one man … successive governments have done little to improve press freedom and as a consequence, we have seen Australia’s slip in world rankings.”