"On balance ... it was the right decision."
Muller said on Tuesday evening he was given a "heads-up" from Woodhouse that he had been given information that "sounded similar" to that given to Walker.
"The next day I had a chat with Michael and we agreed it would be appropriate for him to circle back to Michael Heron and make him aware of that, in case it would be useful for his inquiry."
Muller said Walker and Woodhouse were "very different issues".
"Walker released private, personal and sensitive information to the public, which has cost him his political career. Michael Woodhouse saw this information, and didn't act on it."
He'd now made it "very clear" to his caucus, if they were sent any sensitive information they needed to bring it to his attention as leader.
But he said there was an "absolute distinction" between receiving information, and releasing it publicly.
"MPs receive information all of the time, particularly in opposition. The issue for me is Hamish released it publicly, which is a very serious error in judgment."
On National MP Jian Yang's retirement announcement today, Muller said he had not been asked to leave.
"Not at all, this man had nine years' involvement as a politician. It can be demanding, take its toll, and he signalled that after the election, with his wife and family, he'd like to move on, and I deeply respect that."
His tenure as an MP has been clouded with questions over his links to Chinese spy agencies and his studies at Chinese military institutions.
Yang has always said the associations are above board.
"After careful consideration and talking to my wife and children, I have decided, that after serving three most rewarding terms in the National Party caucus, I will not stand in the 2020 general election," Yang said in a statement this morning.
There had been criticism of Yang for refusing to front for interviews in recent years, but Muller said he disagreed there were any issues with access to the MP.
"Every MP has their own degree of visibility, and the critique he was not available is wrong."
He described the latest absconder from an isolation facility, announced this morning in Hamilton, as a further part of the Government's "shambolic approach".
"New Zealanders have been through far too much for such an ongoing shambolic approach to what is a critical issue for this country.
"For a start, we would have had the right planning for it. The Government has been a week behind regarding demands on the system."
Muller's statements come after another turbulent morning with former National Party president Michelle Boag quitting the party after revelations she sent Covid-19 patient details to another National MP.
National Party health spokesman Michael Woodhouse also confessed this morning to receiving four unsolicited emails from Boag between June 21 and 25 which contained patient details, but it was not the same information that was sent to disgraced MP Hamish Walker.
National health spokesman Michael Woodhouse told leader Todd Muller on Tuesday evening that he was also sent Covid patient data by Michelle Boag.
In his confession this morning, Woodhouse said he was sent four emails from Boag in her capacity as acting chair of the Auckland Rescue Helicopter Trust.
But he believed it was different information from the subject of the Government's inquiry into the leak, but was similar insofar as it contained patient details.
"I was led to believe it was circulating among a number of other health agencies.
"I recognised that the information in those emails was private so I did not share it with anyone else and I subsequently deleted them."
On Tuesday evening, a day after the Government launched an inquiry into who leaked the details of 18 active Covid cases to the Herald and two other media outlets, Hamish Walker confessed that he was behind it. Boag admitted she was his source.
At midday on Wednesday, Walker announced he wouldn't stand for re-election in the Clutha-Southland seat.
Boag announced this morning she had resigned from the National Party because the last few days "have underscored for me the unhealthy relationship I have developed with politics".
She said she had devoted much of life to supporting the National Party.
"Unfortunately this passion has put me on a self-destructive path.
"This was confirmed for me as I wrote to Michael Heron QC last night to advise him that towards the end of June I had sent several emails to Michael Woodhouse comprising notification of a small number of then new Covid19 cases.
"My decisions to share this information were wrong, driven by my distorted view that providing that information would help the National Party to hold the Government to account. In fact it was harmful, not helpful, and it is time that the National Party and I parted ways."
