The Herald revealed last month that Mitchell's parliamentary email account had received 36 emails since December 2023 making allegations against McSkimming, the former Deputy Police Commissioner.
At the time, Mitchell told the Herald the "then-Police Commissioner directed" police staff based in the Beehive office to "refer emails relating to McSkimming directly to his office and not share or discuss them with anyone else in the office".
This meant the emails weren't raised with him, Mitchell said. He said he only became aware of an Independent Police Conduct Authority (IPCA) investigation into McSkimming on November 6 last year.
A memo, seen by the Herald, from the police's ministerial services team to the Police Minister's office last month outlined the process, including that police staff were to treat correspondence about McSkimming "in confidence and not circulate to it others [sic] in the minister's office or police generally".
Correspondence would be referred to the director of Coster's office and managed in consultation with then Deputy Commissioner Tania Kura, the memo said.
The Herald contacted Coster on the night of the IPCA report release, asking for comment on Mitchell's claims about the email protocol, as well as the next day.
However, Coster's office said at the time he would not comment while an employment process was under way with the Public Service Commission. Coster resigned this week as the head of the Social Investment Agency.
This morning, Coster told TVNZ's Q+A programme the first he had heard that police staff had been told to redirect emails about McSkimming was the day following the release of the IPCA report into the handling of complaints about McSkimming.
"I had absolutely no knowledge of that whatsoever. I can't validate whether that was in fact a protocol that was in place," he said.
"But what I can say is there's no way in the world that agency-employed staff in a minister's office are able to prevent the minister or the minister's staff from seeing emails coming in on the minister's email address.
"The role of the agency's staff is to have emails given to them by the minister's own staff to prepare responses for the minister through the agency. There's just no way that police staff in the minister's office could somehow intercept and prevent those emails."
Mitchell today said Coster's claim that "he was not aware about the system instituted to redirect emails is unfathomable".
"The protocol around the emails has been repeatedly verified by several police employees who were given the instruction by Coster's office. It came from his office and most senior direct reports and, as he already accepts, as commissioner, all things ultimately fell to his responsibility."
The Herald in November asked the minister whether Coster was aware of the protocol put in place by the then commissioner's office. Mitchell said that they were "one and the same thing".
In several interviews, Mitchell has explained that emails sent to him are categorised into portfolios - such as police or corrections - by a receptionist and then forwarded to staff in his office with responsibility for the portfolio. These are private secretaries who are seconded from their agencies to the ministerial office.
Mitchell said the office receives a "massive amount of correspondence" and the receptionist wouldn't have read through the emails, other than to identify where they should be forwarded.
Once received by the private secretary, in this case the police staff member, emails about McSkimming would have been sent off to police headquarters without anyone else in the office becoming aware, Mitchell said.
He said that put the police staff member in an "awful situation", but the woman would have believed the allegations were being investigated as they were being sent to the Police Commissioner's office.
Of the 36 emails, 17 were also sent to Mitchell's Whangaparāoa electorate office email. According to Mitchell, those emails were then forwarded to his ministerial office, which he said was the "correct process", with electorate staff not meant to deal with ministerial correspondence.
Coster told Q+A he had seen a file note prepared by the police in recent weeks saying there had been a conversation between the police's ministerial services and the director of his office about what to do with the emails.
He said the "retrospective" file note said that the emails were to be sent to Kura, who was handling them.
"I imagine there will have been some concern across more than one minister's office about where did all these emails go and who saw them and I assume this paperwork was created in response to those conversations."
Police told Q+A the file note was created on November 11 but based on notes from January 2024, which was when some of the emails were being sent.
Elsewhere in the interview, Coster claimed both former Police Minister Chris Hipkins and Mitchell had been briefed by him about an affair McSkimming had.
Hipkins responded by saying he was "never briefed" on McSkimming's relationship while either Police Minister or Prime Minister.
Coster said Mitchell had been briefed on the matter earlier than the minister had said. But Mitchell maintained the first time Coster briefed him, formally or informally, was on November 6, 2024.
Mitchell said Coster was "trying to deflect and relitigate matters" and the former Police Commissioner's "recollections of disclosures in the IPCA report were often found to be inconsistent and unreliable".
The IPCA report made several findings critical of Coster and others. However, it didn't make any finding of collusion or that they had set out to undermine the integrity of the organisation.