Incoming Treasury Secretary Philip Gaetjens has hit back at those who say he should never have been appointed to the role because of his links to the Liberal party, saying public servants should be defined by their ‘own capabilities’.

Labor says the appointment of the former chief-of-staff to Liberal treasurers Peter Costello and Scott Morrison undermines the Treasury department’s reputation, and has accused the government of ‘stacking’ the public service.

But Mr Gaetjens told The Australian Financial Review he is ‘more at the policy end of the spectrum than the political end’.

‘Certainly, there’s a bit too much media focus on defining people by who they worked for rather than defining them by their own capabilities,’ he told the AFR on Monday.

‘As most public servants would know, you do have to combine the art of the possible and look at what can be achieved in the politics of the day, which is getting more and more difficult.’

Mr Gaetjens was also secretary of the NSW Treasury between 2011 and 2015 and served as a senior executive in the Commonwealth Treasury, the Department of the Prime Minister and Cabinet and the South Australian Department of Treasury and Finance.

Treasurer Scott Morrison has said Mr Gaetjens will bring ‘significant experience’ to the job.

Treasury boss John Fraser will step down on July 31.