NSW’s top-ranked public servant will probe a decision to hand a plum offshore trade post to former NSW deputy premier John Barilaro after revelations four candidates were shortlisted for the $500,000-a-year job before it was readvertised and handed to the former senior MP.

Premier Dominic Perrottet has asked the head of the Department of Premier and Cabinet, Michael Coutts-Trotter, to review the decision to appoint Mr Barilaro as the state’s senior trade and investment commissioner to the US, as the outcry to the decision overshadows the party’s budget week.