National Party leader Simon Bridges says the text from a person claiming to be behind the leak of his expense details was "incredibly dark" and "concerning".
Mr Bridges said the text made clear to him that it was from the leaker.
"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 their very clear view in the text message that there would be significant harm to them if the investigation by speaker mallard proceeded.
"It was an incredibly dark, concerning text message."
Mr Bridges said he messaged the person back and made clear his concern was for their well-being.
He said he received expert mental health advice on how to proceed and on Friday, he informed the police.
"On Sunday evening, police contacted me. They made it clear they knew, they had worked out the identity of the person concerned.
"They made clear to me the person was getting the help that they need."
Police did not give him the identity of the person.
"At no time did police tell me that the investigation should not proceed."
"There's been some comment about potentially this person identifying .... specifics about them being in the National Party caucus. There is a range of credible scenarios that really mean I cannot say whether they were or they weren't - [whether they] were a National MP, another MP, someone in Parliamentary Service or indeed wider than that."
The text, which RNZ has not seen, detailed a number of conversations and pieces of information from National caucus meetings over a period of weeks in an attempt to prove the author was a National MP.
Mr Bridges has previously said repeatedly he was confident the expense leak did not come from within the National Party.
The anonymous appeal came after Parliament's Speaker Trevor Mallard launched an inquiry into who leaked the expense details and promised to name and shame the person responsible.
Mr Mallard was contacted yesterday morning about the text message but he refused to comment. Soon after, he announced the appointment of Queen's Counsel Michael Heron to lead the inquiry.
This article was originally published by RNZ.