Both major political parties say an inquiry into the leak of Simon Bridges' expenses would be fine, but they want to get on with the bigger issues.

Questions remain over the leak's origin.

National's Mark Mitchell says the party is 100 percent confident it's not someone within the caucus ... and asks why would the leader be calling for an inquiry if it could embarrass his own.

But Labour's Stuart Nash told Mike Hosking there might be some dissatisfied National MPs hoping to undermine the leader.

"There would be two or three people saying the Party vote is holding up but Simon isn't resonating. Of course you are going to go out with a public face and say you're united. In opposition when you have got a leader polling the way Simon is, there are always MPs talking.

LISTEN ABOVE AS STUART NASH AND MARK MITCHELL SPEAK WITH MIKE HOSKING