NZ First Leader Winston Peters has accused the police of pulling their punches for political reasons in their initial investigation of electoral finance fraud allegations against Act MP John Banks.
Police last night refused to comment while the case is before the courts.
This year police found there was insufficient evidence to charge Banks, police minister from 1990-96, in relation to donations to his 2010 Auckland mayoral campaign.
However after private action brought by Wellington man Graham McCready, the Auckland District Court last week found there was a case to answer and referred the matter for trial in the High Court.
"Along comes a fellow and prosecutes it himself and he gets the judge to agree," Peters told reporters at NZ First's annual conference in Christchurch yesterday.
"The police, with all their legal assets, can't make up their mind. I don't accept that.
"The police need to explain why they pulled their punches on this case."
Peters said the affair revealed "a propensity for the New Zealand police to make political decisions or decisions that reflect that the majority of them may well be voting for one side rather than the other".
He also called for the case against Banks to be heard quickly, rather than having it deferred for months until a High Court date is available.
"It used to be that a person's entitlement to be in Parliament was an issue of great priority so it should be given precedence. There should be no delay here.
"The people's right to know who their properly elected representatives are is a serious issue in a democracy, that's why it should be coming now and not some time later."
McCready has written to MPs asking them to put "the full resources of the Crown" behind the the trial.
McCready said if Solicitor-General Michael Heron elected not to take over the case, he would continue to handle it himself.