Self-styled public watchdogs Penny Bright and Graham McCready claimed their biggest scalp yesterday as Act MP John Banks was found guilty of filing a false electoral return.
But police reluctance to pursue the affair has fuelled calls by Ms Bright and David Bain's champion Joe Karam for an independent commission against corruption.
Retired Wellington accountant and serial litigant Mr McCready kick started the case against Mr Banks by bringing a private prosecution against him after police decided not to prosecute despite finding evidence of an offence.
Outside the High Court at Auckland yesterday he said he was ecstatic with the verdict.
Ms Bright who claimed she and friend Lisa Prager made the original complaint to police said she felt vindicated by yesterday's decision.
Ms Bright had previously faced off against Mr Banks over his involvement with Huljich Wealth Management which was found to have misled investors.
"I've never actually met a person whose signature is so meaningless", she told the Herald last night.
"What we lack in this country is an independent commission against corruption and I think it's a disgrace that it took ordinary committed citizens to get this matter to trial."
Ms Bright said she had heard a recording of the original police interview with Mr Banks over the campaign finance issue, and "as far as I'm concerned they had more than enough evidence for the prosecution to go ahead.".
"The track record here is it seems Ministers of the Crown are a form of protected species and I think this historic an unprecedented court case has proven they're not. Justice was done and seen to be done but I think the main reason for that was the world was watching."
Labour MP Trevor Mallard who also claimed to have written the original letter of complaint to the police said yesterday's verdict, "shows we have a robust justice system in New Zealand even if it's one that works at glacial speed".
"It also shows that it doesn't matter what position someone holds, in the end it is possible for them to be convicted and that's not the case in a lot of countries even other western countries."
He hoped the case would cause police to review their methodology.
"Corruption cases are serious but also if that sort of methodology was creeping into crimes against people, assaults rapes and murder then I would be very very concerned."
Mr Karam noted that the police investigation into Mr Banks campaign finances found insufficient evidence to bring a prosecution.
"Yet again it took a member of the public to fight to see justice done."
"A much bigger question arises from all this - does New Zealand need a body similar to that operated in New South Wales, Australia to expose and prosecute corruption by those in the public service?"
A spokesman for police refused to discuss any aspect of the case, saying no comment would be made until after sentencing.
Meanwhile, Mr Mallard said yesterday's verdict was "a sad end to what's been a long and interesting career even if most of the time I haven't agreed with John Banks".
"Banks is someone who dragged himself up from an awful start in life and I think a lot of people including myself have had admiration for what he'd done there and also I would note while you can't forgive corruption is the fact he was a leading light even as recently as a month or so ago in the overturning of the legal highs regime. He's always been controversial, often wrong but certainly always a character."