This week on Inside Parliament, 1 NEWS reporters Maiki Sherman and Mei Heron discuss the latest developments of the leaking of National leader Simon Bridges' travel expenses.
Ms Sherman said it had developed from a "whodunnit, to a who the heck dunnit", after an anonymous text message was sent to Mr Bridges and Speaker Trevor Mallard confessing.
National on Tuesday announced it would launch its own internal inquiry.
Mr Bridges told 1 NEWS the point of the inquiry was to determine if the leaker was from within National.
"It is possible the leaker is a National MP or a staffer, but the point is we don't know. It could be someone within Parliamentary Service or wider within Government."