Simon Bridges reveals the details of the text messages he received from the person who claims to have leaked MPs' expenses.

The Speaker has called off an inquiry into the leaking of Simon Bridges' expenses details, saying he believes the perpetrator is from within the National Party.

A person claiming to be National Party caucus member has sent anonymous texts imploring both the National leader and Speaker Trevor Mallard to abandon the investigation, citing mental health issues. Police have uncovered the identity of the person, but would not reveal their identity.

However Mallard had confirmed in a statement he had called off the inquiry, claiming he was satisfied the leaker was unlikely to be anyone outside of National.

ROBERT KITCHIN/STUFF National Party leader Simon Bridges says he still doesn't know the identity of the person who leaked details of MPs' expenses.

In a press conference earlier in the day, Bridges said it was important that person received all the help they needed, but the integrity of Parliament had to be protected too. However, he had climbed down from the staunch claims he made last week that he did not believe it was a member of his own caucus.

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"There are a range of credible scenarios that really mean I cannot say whether they were, or whether they weren't. Whether they were a National MP, another MP, someone in Parliamentary Services or indeed wider than that."

Bridges said he could also not rule out the text as an attempt to manipulate the system.

However, Mallard indicated that while an independent investigation would not go ahead, Parliamentary Service would cooperate with an internal National Party inquiry.

"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. 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," Mallard said.

MURRAY WILSON/STUFF The finger for the leak has been pointed at Labour as well as at the National ranks.

"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 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. The general manager will make any relevant staff emails available," said Mallard.

The wellbeing of the person was also Bridges' "utmost concern", but on speaking with police he said he was satisfied the inquiry could proceed. He said police had informed him there was no immediate danger of physical harm.

"What's also really important is the integrity of the Parliamentary system. It's not about the National Party, the Opposition, it's about everyone having confidence in the integrity of the Parliamentary system."

Bridges said the person made contact last Thursday saying they feared exposure because they had ongoing mental health issues. He contacted police, who confirmed on Sunday that they had identified the person who sent the message. Bridges said he didn't know who the person was.

The party also sought advice from mental health professionals as to how to handle the situation.

The anonymous text message was sent to the National leader, as well as Mallard and a media outlet. In it the author claimed to have leaked the report to Newshub but also asked not to be identified.

Bridges confirmed the text stated that the leaker was in the National caucus.

"It also made quite clear that this person had a prolonged, serious mental illness and serious issues in relation to that, and their very clear view that there would be significant harm to them if the investigation by Speaker Mallard proceeded.

"It was ultimately, an incredibly dark, concerning, text message," Bridges said.

Police informed Bridges they were working on the assumption that the investigation would continue, and would ensure the person had the support they needed. They would not reveal the identity of the person.

In a statement, a police spokesperson confirmed Bridges' details and outlined the police handling of the matter.

"The information provided by the National Party did not identify the individual, however their identity was established through subsequent police enquiries.

"Steps were taken as they are for any matter reported to police where there are immediate concerns for the welfare of an individual. The National Party was advised that Police would not disclose the individual's identity for privacy reasons."

Police were handling the issue "entirely from a mental health perspective", the spokesperson said.

If Heron, or others involved in the inquiry, had questions for police, they would be "considered on the basis of privacy principles, and police may seek advice as required regarding such requests".

It's understood the person said they leaked the information because they disagreed with Bridges' leadership and wanted him to be held responsible for "wasting" taxpayers' money, RNZ reported.

The investigation, headed by former solicitor general Michael Heron QC, could end up costing taxpayers upwards of $50,000 based on previous similar inquiries.

Bridges said he was "very worried" by the text and sought advice from senior colleagues.

"I messaged the person back and made clear my concern and that my utmost concern was for the wellbeing of this person. Later that day we received significant expert mental health advice on how to proceed with this matter and on Friday I informed the police."

Newshub reported earlier this month that Bridges had spent more than $100,000 on travel and accommodation over the past three months. It's understood that Newshub was also sent the text but decided against reporting it for the wellbeing of the texter.

Newshub can verify that a text message was sent from the leaker to Simon Bridges and the Speaker urging them to call off the inquiry. I think it’s beyond appalling that details of the text have been leaked and reported on given the mental health issues involved. — Tova O'Brien (@TovaOBrien) August 23, 2018

Mallard has declined to comment on the text.