Mr Banks' lawyer David Jones QC says he will be making an application for a discharge without conviction. Until a court decision on that and Mr Banks' sentencing on August 1 - the day after Parliament rises for the September election - he and the Government will face Opposition attacks over his continued presence in Parliament.
National Party-aligned blogger David Farrar yesterday wrote that would be "a significant distraction for the Government".
While it was a decision purely for Mr Banks who had every constitutional right to stay on until a conviction was entered, "I think John Banks came into politics with very honourable motives, and I think resigning would be in the same spirit".
Neither Mr Banks nor Act Leader Jamie Whyte returned the Weekend Herald's calls yesterday, but Mr Prebble said he "wouldn't think for a minute" that Mr Banks would prefer to resign before a decision on a conviction.
"Mr Banks has been elected to Parliament and as such the people of his electorate are entitled to have a Member of Parliament. He hasn't been convicted, he may not be convicted, and as such he should continue being a member of Parliament."
Mr Prebble also downplayed the seriousness of the offence Mr Banks had been found guilty of, which carries a maximum penalty of two years imprisonment.
"We're acting as though this is some heinous crime. No it isn't, it's just a clerical error".
Mr Prebble said the affair had "probably" had an effect on Act, but in a recent Roy Morgan poll taken while Mr Banks' trial was proceeding, the party's support rose while that for Labour and the Greens went down.
"If he was to quit as a member of Parliament when he hasn't been convicted, that might damage Act's brand."
Mr Banks' friend and supporter in court this week Michelle Boag, said she didn't know whether he intended resigning.
"I'm sure he hasn't made up his mind about that yet, obviously he's got a lot of things to think about, and he's got to take legal advice on his position."
Prime Minister John Key said Mr Banks' immediate political future was not something he could comment on.
"Ultimately that's a question you have to direct at Mr Banks.
"He's got a number of options available to him."
Asked what his advice to Mr Banks would be, he replied: "The reality is I can't offer him advice any more than I could offer David Cunliffe advice on whether he should resign".
Meanwhile, Royal Federation of NZ Justices' Associations registrar Alan Hart confirmed any JP convicted of a crime punishable by imprisonment is compulsorily deregistered if they don't resign before then.
When asked whether Mr Banks should resign, Dr Whyte yesterday told National Radio he wanted his sole MP "to follow due process".
Dr Whyte said he hadn't been in touch with Mr Banks since the verdict and "I'm not quite sure what his intentions are on this".
He hadn't spoken with Mr Banks because "these events don't really concern the Act Party".
"John isn't involved in our campaign, he isn't going to be an MP after the next election and this is as far as we're concerned because this was to do with his mayoral campaign.
"This is not an Act Party issue," Dr Whyte said.
