A senior ministerial adviser who quit over his part in the "budgie nine" scandal was initially hired to answer phones and do some diary work, Peta Credlin says.

Former prime minister Tony Abbott's chief of staff said she would have thought that Jack Walker, 26, wasn't up to the position he eventually filled, policy adviser to defence industry minister Christopher Pyne.

Mr Walker and eight friends attended the F1 Grand Prix in Sepang, Malaysia, celebrating Australian Daniel Ricciardo's win by stripping down to their budgie smugglers emblazoned with the Malaysian flag.

They spent four nights in a Malaysian jail before being cautioned and released. Mr Walker resigned at the weekend.