The "chatter" around Parliament is that Simon Bridges' expenses details were leaked by one of his own MPs, says Labour's Michael Wood.
Newshub on Monday revealed the National Party leader spent more than $100,000 in just three months on travel and accommodation. The information wasn't due to be released until Thursday, but was leaked to Newshub political editor Tova O'Brien, who won't reveal her sources.
An inquiry has been launched to find the culprit.
"There was a bit of chat around Parliament about someone yesterday, but we don't really know," Mr Wood told The AM Show on Friday, saying there was a "lot of chatter" around a National MP.
Mr Wood wouldn't name names - perhaps because he was sitting right next to Judith Collins, who unsuccessfully challenged for the leadership earlier this year, has shown up in Newshub's preferred Prime Minister rankings only a few points behind Mr Bridges, and - going by "chatter" on social media - is the public's number one suspect.
She said it "absolutely" wasn't her, and when the forensic experts check her computer, they'll find "nothing to see".
"I'll just be gutted if it's someone in our party. I don't know who it is," she told The AM Show.
Ms Collins wouldn't name any suspects.
"I've learned never to do that. Just wait and see."
Asked if it turned out to be an MP, if they should resign, she didn't say yes or no.
"Let's have a look, but I'd be really gutted if it's somebody who's breached the trust of [inaudible]."
Mr Wood said the uncertainty was creating distrust amongst MPs and their staff.
"It's a little bit like sort of being at school and the teacher knows someone's done something naughty, and everyone's under suspicion until they've found the person."
Speaker Trevor Mallard will approach the Queen's Counsel to initiate an inquiry.
"My view is that if something was actually forwarded from an MP's machine or a staff member's machine to a news organisation, that shouldn't be too hard to identify," he said on Wednesday.
He said the leak had to have come from either himself, Parliamentary staffers or the National Party caucus, all of whom were supplied the information. He said it's not believed hacking was involved.