The Speaker Trevor Mallard has called off an inquiry aimed at identifying who leaked National leader Simon Bridges expenses.
The inquiry was launched after a call from Mr Bridges to weed out the leaker, in the interests of maintaining public confidence in those elected MPs.
But Mr Mallard has called off that inquiry after the alleged leaker texted Mr Mallard and Mr Bridges claiming responsibility for the breach.
The texter, who didn't reveal their identity, said they were a National Party MP, and being outed in public would seriously damage their mental health.
"The existence of, and part of the detail of, a text both the Leader of the Opposition and I received last week has been reported on," Mr Mallard said.
"It has now been confirmed to me that the person who leaked the details of the expenses and the texter are the same person.
"He or she has details of events that it is unlikely anyone outside the National Party would be privy to.
"The text is from someone who is clearly very disturbed and today's publicity will almost certainly make that worse.
"My priority is to get appropriate support to them whether they are an MP or a staff member.
"I have discussed my decision with Hon Simon Bridges. He disagrees with it. He wants the inquiry to continue.
"I have indicated to him that the Parliamentary Service will cooperate if he decides that he wants to proceed with an investigation and appropriate consents from MPs are in place."
Police know alleged leaker's identity but won't tell Simon Bridges
Mr Bridges, at an earlier press conference, said police knew the identity of the person who messaged him but they would not divulge their identity.
Mr Bridges confirmed that he received an anonymous message last Thursday from a person claiming to have leaked the information.
The author had also said that they suffered from mental health issues and "significant harm" would come to them if the inquiry into the leak continued, Mr Bridges said.
The opposition leader said he had informed the police of the message on Friday after receiving "significant expert mental health advice on how to proceed with this very concerning matter".
"My utmost concern was for the wellbeing of this person," Mr Bridges said.
On Sunday evening, police contacted Mr Bridges saying they knew who the person was and that they were receiving treatment for their mental health issues.
Police said there was no safety issue for the person.
"I asked specifically in relation to Mr Mallard's investigation what the position would be there if it proceeded and at no time did police tell me that the investigation should not proceed," Mr Bridges said.
"They made it clear in fact that they were working on the assumption it would and if that was so, they would inform the person in question about that to ensure they had any specific help and assistance and support that they would require."
Mr Bridges said police would not reveal the identity of the person despite the opposition leader asking.
"They gave me nothing from which I could deduce who the person was, their view was unless there were specific overriding factors such as safety, they were not going to disclose that in the interests of privacy," he said.
"There's been some comment about potentially this person identifying that they…specifics about them being in the National Party caucus.
"There is a range of credible scenarios that really mean I cannot say whether they’re a National MP, another MP, someone in parliamentary services or indeed wider than that.
"Ultimately, I don’t know who this is."