Mallard cancelled the Heron inquiry after it was publicly revealed that he, Simon Bridges and Newshub had received a text from the leaker claiming to be a National MP, containing reference to matters relating to caucus meetings, and pleading for an inquiry not to be held on the grounds of mental health.
Mallard said tonight he could tell from the text that was sent to him, Newshub and Simon Bridges "that it was 99.9 per cent certain that it was someone exceptionally close to National - either an MP or a staff member who could have had access to caucus things or overheard a number of conversations.
"But because I had been accused of being the leak, I wanted to make certain that my records were searched, which they wouldn't be under the National Party's [inquiry] and to make sure that the staff responsible within the Parliamentary Service and my office were properly checked as well."
Asked who had accused him of being the leak, Mallard said Bridges had when he referred to the term "the Speaker's office" as being one of the potential sources.
"That was code for me.
"And he said me to numerous people privately."
Mallard said he did not announce the private inquiry at the time because he was trying to get the whole issue out of the media.
"The nature of the text was that there was – there is – someone with a serious mental health issue and I just wanted to get it out of the media. I didn't want to be involved. A somewhat forlorn hope."
He had kept it secret from National until it was over because "if there was a problem, I wanted it dealt with".
Mallard tonight released the privacy waiver that he and relevant staff who had access to the leaked material had signed for the KPMG inquiry. Anyone who had opened the document, or printed or copied or scanned it would have been identified.
He also released the Parliamentary Service memo outlining the findings which included the following: "On the basis of this independent review, there is no evidence that staff in the Office of the Speaker, Mr Speaker, or Parliamentary Service finance and corporate staff released details of this quarterly expense disclosure report to any unauthorised parties."
Asked why he had not cancelled the Heron inquiry after receiving the text about the leaker's mental health, Mallard said that to have cancelled it using the material in the text "would have drawn attention to and pressured the individual who has severe mental health issues and we had hoped to keep the text confidential".
Once the text and parts of it had been leaked to RNZ it was no longer confidential and the previous reason for not cancelling it no longer applied.
It would not have been appropriate for the National Party inquiry which is being funded out of the National leader's budget to have included the Speaker, he said.
National deputy leader Paula Bennett, who is overseeing National's leak inquiry, said tonight that she had known about the private inquiry for several weeks after Mallard told her.
"The Speaker's inquiry, which he had publicly stated he was not having, is a matter for him. The National Party is conducting its own inquiry and will comment on that once it has concluded."
It received the final set of relevant information from Parliamentary Service only last Friday.
She said Bridges stood by his claims there were a number of possible source of the leak.
National MP Jami-Lee Ross went on leave last week citing personal health issues, it was announced last week by Bridges and Bennett, but Bridges said Ross was adamant he was not the leaker.
TIMELINE
August 13 - Newshub publishes a story based on Simon Bridges' leaked expenses
August 15 – Speaker Mallard agrees to hold inquiry
August 16 – Bridges, Mallard and Newshub receive anonymous text message allegedly from National MP pleading for inquiry to be called off on mental health grounds.
August 17 - Bridges talks to mental health experts and tells police about text on advice.
August 19 – Police tell Bridges they have identified and contacted the texter (wont name them) and that the person is getting support.
August 23 - Mallard names Michael Heron QC to conduct inquiry
August 24 – RNZ reveals that texts were sent the previous week to Bridges and Mallard, Ardern and other comment publicly.
August 24 - Mallard cancels Heron inquiry.
August 28 – On Mallard's request. Parliamentary Service starts an investigation into himself and PS staff who access to the travel expenses, using KPMG.
September 4 - Parliamentary Service reports that KPMG finds no evidence of any disclosure of the information to unauthorised parties.