A redacted version of the letter was tabled in Parliament by former Labour Party leader Cunliffe in February last year, leading to then-Tertiary Education Minister Steven Joyce and the Tertiary Education Commission (TEC) seeking information about WITT.
Cunliffe said it would not be appropriate for him to comment as he was no longer an MP, referring inquiries to Labour's current tertiary education spokesman Chris Hipkins.
"Members of the public should be free to communicate with Members of Parliament without the fear that they will find themselves in hot water. It's an important part of the democratic process," Hipkins said.
"I'm concerned that WITT have gone to the lengths of engaging handwriting experts to identify the author of the letters. Whatever the contents of the allegations, as a public institution they should be willing to answer them rather than conduct a witch-hunt to find the person making them."
As a result of the TEC process, WITT chief executive Barbara George saw an unredacted version of the letter, which was signed "F Jacks".
In May 2016 another letter with the same name was sent directly to Joyce, which made various negative observations about WITT and its then-chairwoman, Mary Bourke.
Letters were also sent to the TSB Community Trust and the Bishops Action Foundation, with which Bourke was associated.
"Ms Bourke ... unsurprisingly, was less than impressed," the ERA decision said.
Parr had worked at WITT for about six years until 2013 when she left after a personal grievance application. That was resolved through a mutual agreement, which included the condition that she "not make any negative or disparaging statement publicly about WITT or any of its officers or employees", according to the ERA decision.
Bourke showed the second letter and the hand-written envelope to chief executive George, who recognised the writing as Parr's.
She sent copies of the letter and envelope to three handwriting experts, along with various documents from Parr's file for comparison.
All three concluded that the writing was probably Parr's. One of the experts, Patricia James, was a senior document examiner at Police National Headquarters with 20 years' experience.
She said that "the author of the specimens attributed to Angela Parr completed the address on the questioned envelope and the printed entry at the top of the questioned letter".
WITT called on Parr to desist with her activities, but she denied being the author.
Nonetheless, she argued that letters sent to ministers should not be considered public and therefore did not breach the 2013 agreement.
The authority disagreed.
"Ministers are public officials but in any event it is difficult to say there has been no publicity when, as occurred with the February letter, the result is inquiries by public agencies and questions in the house," said authority member Mike Loftus.
He could "readily" conclude that Parr was the author and that the letters were negative and disparaging.
Parr had acknowledged that she still harboured grudges against WITT and Bourke and admitted she'd had further correspondence with Cunliffe about matters involving the institution.
"I have accepted there has been a breach [of the 2013 agreement] for which Mrs Parr is responsible. I also accept that given the attempt to hide the breach by using an alias it was deliberate," Loftus said.
Parr was ordered to pay WITT a $6000 penalty by September 6.
Parr told the Herald she was still bound by the 2013 agreement so could not comment. However, she said she disagreed with the ERA's decision and was considering an appeal.
A WITT spokesman said the institution did not wish to make further comment as the matter had been determined.
