National MP Judith Collins wants to know who leaked National leader Simon Bridges' roadshow expenses to Newshub, and believes Newshub's political editor Tova O'Brien has the answer.
"I just thought it was a pathetic attack," Ms Collins told The AM Show on Wednesday.
The National Party leader’s expenses were leaked to Newshub on Monday night, which revealed Mr Bridges spent $113,000 on Crown limos and accommodation in the past three months.
We don't believe it's anyone in the National Party.
"You guys are great - you come along and ask us who did it when you know who did it," Ms Collins said when Garner asked if she knew who had leaked the information.
"I don't know who did it," Garner said, to which Ms Collins replied, "Tova does".
"We don't believe it's anyone in the National Party and that's why we really do want to get to the bottom of this and we want to find out who had that information and who gave it to Tova O'Brien," Ms Collins said.
"I think that Tova does know who leaked the information, and she's made a couple of comments to our people that have certainly made us think in a particular direction, and it's definitely not the National Party."
National has called for an independent investigation to find out who leaked the expense details.
The entire National Party caucus had seen the expenses, after the whips and Leaders Office received the information last week. Members of Parliamentary Services may have also seen the details.
Ms Collins says she wants suspicions cleared, after some had pointed to Speaker Trevor Mallard as a possible leaker. But Prime Minister Jacinda Ardern hit back on Tuesday, saying Mr Mallard is "impartial" and it's a "serious allegation".
Ms Collins said she and Trevor have "had our run-ins in the past". She once sued him for defamation. Having said that, Ms Collins added she doesn't want to have the speaker's office or ministerial service or parliamentary service "in doubt as to their integrity".
"I realise that outside of Wellington a lot of people won't think it's that important, but it is important because it goes to democracy and it goes to the fairness and integrity of the parliamentary system," she said.
"We trust the parliamentary service, ministerial service and the speaker's office with a lot of private information and I think we do need to know where this came from."
Both Mr Bridges and Jacinda Ardern are standing behind their caucuses, asserting confidently that the leaked information didn’t come from either National or Labour.
Mr Bridges spent $919 a day - more than people earning the minimum wage take home in a week. Former Opposition leader Andrew Little spent $35,000 less than Mr Bridges over the same time last year.
But Ms Collins said leading the opposition is the "hardest job in the world", and that Mr Bridges was just trying to do the right thing by getting out and meeting New Zealanders.
Watch the full interview with Judith Collins above.
The AM Show with Duncan Garner, Amanda Gillies and Mark Richardson, weekdays 6-9am on RadioLIVE and streaming live to the rova app on Android and iPhone.