John Banks says the Solicitor-General should stand aside while an independent investigation is carried out into his involvement in Mr Banks' failed case.
The Court of Appeal today cancelled its earlier order that Mr Banks should be retried on a charge relating to election expenses and has instead acquitted him.
The former Act leader, police minister and Auckland mayor was convicted last August of failing to declare two $25,000 donations from internet entrepreneur Kim Dotcom during his mayoralty campaign in 2010.
He appealed against that conviction after his wife found evidence proving that two American businessmen had attended the lunch on 5 June at which Mr Dotcom originally said the donations were discussed.
Mr Banks said Solicitor General Mike Heron QC should stand aside while the Attorney General, Chris Finlayson, investigated him.
He said he wanted to know when Mr Heron found out about the new evidence, and if he did not know about it, why not.
The Dean of the Canterbury Law School Chris Gallavin said Mr Heron should step aside while the investigation occurred.
"It might even be for the integrity of the position and for the comfortableness of him actually conducting his daily duties, it might be best for him to step aside while this review is being conducted by the Attorney-General."
Three years of 'hell'
Mr Banks said the truth had prevailed after three years of "hell" going through the courts.
During a tearful news conference this afternoon, Mr Banks said people had no idea how punishing and lonely the process had been.
He said it was also incredibly stressful on his family and friends.
Mr Banks said he did not know why the case was conducted the way he felt it was.
John Banks addresing the media after the Court of Appeal cancelled an order he should be retried on a charge relating to election expenses Photo: RNZ / Diego Opatowski
"I've been very disappointed in the Crown this prosecution became very personal and very vindictive.
"Witness the Court of Appeal judgement - a serious miscarriage of justice, why? I'm not sure, and we might never know."
Mr Banks said he held no malice, but had yet to consult his legal team on whether he would take any action.
A timeline of John Banks' life
The Crown asked a barrister, Rowan Butler, to interview Mr Dotcom about the lunch and Mr Dotcom accepted the Americans' evidence was correct.
However, he reverted back to his original account, saying the lunch with Mr Banks occurred on 9 June, the same day the cheques were written.
Following that interview, Mr Butler provided a memorandum to the Crown saying Mr Dotcom changed his statements and that the donations were discussed at the second lunch.
However at the appeal hearing last October the Court was not told about Mr Dotcom's change of story.
The Court of Appeal judges said that had they known of Mr Butler's memorandum, they would not have ordered a retrial, and that the Crown's failure to disclose it had caused a miscarriage of justice.
The Court said it was satisfied the Crown's 'serious error of process' was an error of judgement rather than misconduct.
Act Party leader David Seymour said there could be a place back in the party for Mr Banks.
Mr Seymour, who replaced Mr Banks as Act's Epsom candidate after Mr Banks stood down from Parliament would not rule out a return to the fold for the former MP.
"Ah look, it's very possible, he will always remain a friend, but I'm sure he's working out what he wants to do after a momentous decision."
Mr Seymour said he had not yet spoken to Mr Banks about the court decision.
The man who brought a private prosecution against John Banks in 2013 said he was not disappointed at the decision.
Retired Wellington accountant Graham McCready said it was right to throw the case out if the procedure is not correct, regardless of guilt or innocence.
Mr McCready said he would continue to pursue private prosecutions.
Attorney General looks into Banks decision
Meanwhile the Attorney General Chris Finlayson said he would looking into today's Court of Appeal decision.
He said as the Attorney General he stays out of criminal matters, and the Solicitor General briefed the job to someone else because it was a criminal case involving a politician.
"Decisions were made by that person on the way in which the case should be conducted and the court of appeal has been critical of that aspect of it.
"So broad terms the Crown carries the can, as it were, but there are matters of concern that Crown Law will be wanting to be look at."
