A level of understanding from the Prime Minister for Simon Bridges' big domestic travel bill.

The opposition leader's racked up a six figure bill over the last three months, which included his nationwide roadshow.

Jacinda Ardern told Mike Hosking she knows how quickly those costs can add up - admitting she was surprised at how high her own travelling expenses had been, when first appointed party leader.

The figures for all MPs are due to be released later this week, but Bridges' was leaked yesterday.

Jacinda Ardern says she has no idea of who or where the source might be.

"Parties have it made available to them at their own expenses, so that's probably a question better asked on the National Party."

Just over $80,000 of that has been on road travel, partly spent on a 'getting to know Simon' nationwide tour.

Bridges told ZB he doesn't know where the leak came from - but he's confident it didn't come from his caucus.

"We'll see what the situation and hopefully the truth will come out over time."

 

LISTEN TO JACINDA ARDERN TALK WITH MIKE HOSKING ABOVE