The acting chief executive of Corrections, Rachel Leota, also called her to apologise.
In a statement to the Weekend Herald, Leota said her department was not advised, or consulted, by the Corrections manager before the correspondence was sent to Haumaha.
"This is not acceptable and I will be apologising to the former staff member and offering her our support."
Leota said Corrections only became aware of the correspondence when it was being prepared for disclosure to the Government Inquiry by Mary Scholtens QC.
"It was addressed at this time with the [former staff member's manager] and a decision was made not to take any further action," Leota said.
"However, I have asked that this be looked at again."
The email from the Corrections manager was sent to Haumaha in early August as the Herald was investigating the allegations of bullying made by the former Corrections staff member.
She was one of three women - two senior policy analysts from Justice and one from Corrections - working on a joint project who left Police National Headquarters in June 2016 and refused to return because of Haumaha's alleged verbal bullying.
According to the IPCA, Haumaha telephoned the Corrections manager and asked him to provide his recollection of the project, the team members involved and specific information about the former Corrections staff member.
The Corrections manager sent an email to Haumaha with a document which was not on official department letterhead.
"It set out his observations about the [the complainant's] behaviour, and confidential details about what he believed to be her performance and employment status in the Department. The document was critical of [the complainant].
That same day, Haumaha forwarded the email to his lawyer and advised this was the response from Corrections regarding the bullying allegations that had yet to be published by the Herald.
"This is exactly what I asked Police to do to be more proactive and prepare a response in the event [the New Zealand Herald journalist] came out with his usual rubbish," Haumaha wrote in the email.
Over the next few days, Haumaha emailed the document to three of his staff and a member of the Māori Focus Forum - a group of senior Māori elders.
The influential Māori leader subsequently contacted one of Haumaha's staff to urge him to support Haumaha.
Haumaha denied sending the email to discredit the complainant, telling the IPCA he was "trying to put the incident in its perspective and just to make people aware that, you know, you know, these allegations against me, there needs to be some context around it".
The IPCA asked whether Haumaha if it was appropriate to send an email containing personal information about another agency's employee to members of his team.
"Yeah and I don't know why that happened, I suppose in a, in a moment of stress, pressure, whether I sent that, and yeah to tell you the truth, I can't even recall sending them the, the email," Haumaha told the IPCA.
The IPCA noted: "This seemed at odds with what he had just disclosed was his motive."
The Herald published the story and two of the three women involved later made complaints which were investigated by the IPCA.
The IPCA upheld their complaints although Haumaha's behaviour towards the former Corrections staff member was considered "not unreasonable" on two incidents.
On another incident, she contributed to the argument but the IPCA found Haumaha was determined to assert his authority and did so "loudly, aggressively and argumentatively".
One of Haumaha's senior staff members intervened twice.
"His behaviour, in entering into an argument in front of other staff and members of the team, and in asserting himself as he did [including by putting his leg on the chair immediately in front of [the complainant], was inappropriate and unprofessional," the IPCA wrote.
"On any reasonable view of it, it was intimidating, whether it was designed to be or not."
The IPCA found Haumaha's behaviour could be described as bullying, in the common use of the word, but not to the standard of workplace bullying.
Because the "clearly inappropriate behaviour" didn't meet this threshold, the Prime Minister Jacinda Ardern said she was given legal advice Haumaha could not be sacked.
Instead, the matter will be treated as an employment issue by Police Commissioner Mike Bush.
Haumaha will return to duties in the new year.
