John Banks has lodged a complaint against the Queen's Counsel who prosecuted the politician for electoral fraud.
The parliamentary career of the former Act leader ended after he was convicted in the High Court for not disclosing two $25,000 donations from internet mogul Kim Dotcom to his Auckland mayoralty campaign in 2010.
The Court of Appeal then quashed the conviction after the "obsessed" detective work of Mr Banks' wife, Amanda, who was stung by the trial judge's opinion of her credibility when he preferred Mona Dotcom's evidence about a lunch which was crucial to the case.
Mrs Banks tracked down two witnesses from America who corroborated her version of events and whose evidence the three appellate justices said was "likely to have changed the outcome of the trial", if accepted.
What the three appellate judges - or Mr Banks' lawyer David Jones QC - were not told was that Dotcom, when presented with the the evidence of the two American businessmen, changed his evidence.
There were now two lunches, he said, and the American businessmen were at one of them.
These comments were contained in the now infamous "Butler memorandum" which the Crown failed to disclose.
In a later judgment, Justice Forrest Miller said the Crown could not both withhold the memorandum and oppose the appeal on the grounds that it did.
"The effect was to mislead the court ... we are satisfied that there has been a serious error of process. It is, we accept, attributable to an error of judgment rather than misconduct."
The appellate judges found they would not have ordered a retrial had they known of the Butler memorandum, so a miscarriage of justice had occurred.
They recalled the earlier judgment and ordered there would be no retrial, which has the effect of an acquittal.
"It is important to bear in mind that it was by no means certain the appeal would succeed. Only in hindsight does that result seem obvious," Justice Forrest Miller said in the Court of Appeal judgment.
"Had we rejected it on the grounds that it lacked cogency or the defence could have called it at trial, the appeal would have failed."
Since then, the Crown conceded Paul Dacre QC, an independent barrister who prosecuted the case, should have disclosed the Butler memorandum ahead of the appeal hearing.
The Crown therefore agreed to pay Mr Banks' legal bill, $66,200, incurred from that point on.
"Mr Dacre decided that the memorandum from Mr Butler was not disclosable in relation to the appeal but would be in the event a new trial was ordered. This was an error of judgment," John Billington, QC, wrote on behalf of the Crown in documents lodged in the Court of Appeal.
The documents show Mr Banks, who is seeking another $190,000 in legal costs from the trial, also signaled his intent to lay a complaint against Mr Dacre with the New Zealand Law Society.
"Something which has really bothered me is the thought that the Butler memorandum may never have been disclosed at all if the original appeal had not been successful," Mr Banks wrote in an affidavit filed with the Court of Appeal.
Mr Banks confirmed to the Herald he laid a complaint with the Law Society, although Mr Dacre said he had no "knowledge of the complaint and therefore no comment".
A Law Society spokesman said he could not comment on a specific case, but generally speaking, a complaint will be sent to the Standards Committee for consideration.
At the same time, a copy will be sent to the lawyer being complained about and they have the right to make a written submission to the Standards Committee.
A complaint may be looked into, resolved by negotiation, or the Standards Committee may decide to take no action.
The saga so far
April 2012: Kim Dotcom's $50,000 of anonymous donations to John Banks' mayoral campaign in 2010 become public.
July 2012: Police do not lay charges after investigation.
November 2012: Graham McCready takes private prosecution against the Act MP.
October 2013: Banks resigns as a Minister after Judge Phil Gittos rules he should stand trial.
June 2014: Banks found guilty after a High Court trial. Later he resigns from Parliament.
November 2014: Banks is successful in overturning the conviction in the Court of Appeal.
January 2015: Solicitor-General Mike Heron, QC, confirms a new trial. Scheduled for July.
March 2015: Banks' lawyer David Jones, QC, seeks to have charge dismissed after the late disclosure of new material from the Crown.
May 2015: Court of Appeal recalls judgment and orders no retrial. Banks is acquitted.
March 2016: Awarded $66,200 in costs for Court of Appeal hearing. Seeking another $190,000.
May 2016: Banks lays complaint against Crown prosecutor Paul Dacre, QC, with Law Society.