A proposal for 10 local authorities to move to online voting at next year's elections is seriously flawed, an IT expert says.
Five councils have already signed up to the trial, with a further five, including Christchurch, Wellington and Hamilton, yet to decide.
Local body elections are currently carried out via postal voting.
Local Government New Zealand, which proposed the trial, said online voting would future-proof elections from the eventual demise of postal services.
President Lawrence Yule said an increasing number of activities were carried out safely online and there was no reason why voting should not be as well.
"If we took the worry about fraud or hacking to its logical extreme, then nobody would use online banking for instance, and people do by their millions. So I think it's a matter of balancing up the risks and the benefits of this."
An IT expert, who has previously advised the Government on security problems with online voting, said the trial carried a lot of risk in return for very few benefits.
Dave Lane said there was currently no way to guarantee an online voting system would be safe from a hacking attack.
"It is possible, for a trivial amount of money ... to engage sufficient computing resources internationally to completely knock over any online or electronic voting system we have, just for fun."
He said an online vote was no longer a secret ballot, because of the need to verify that somebody was who they said they were before they were provided with a password allowing them to vote.
"With online voting, you cannot do something ... which is guaranteeing the anonymity of a voter, so that a voter can feel as though they can make whatever vote their conscience dictates and not have any ramifications, if the Government decides that they want to take action against people who didn't vote in the way they wanted them to vote."
Another IT expert, Stephen Judd, said there were numerous examples overseas of online voting systems being hacked.
He said luckily most of these had been carried out by people wanting to alert authorities to problems with their systems, but that it was just a matter of time before an election was derailed.
"If I wanted to disrupt an online election, I would perhaps send out spam email purporting to come from the council with fake links to an alternative voting site.
"That doesn't even attack the system itself, it just attacks people's trust in the system."
Last year, an Australian parliamentary inquiry found there was no way to introduce online voting without "catastrophically compromising our electoral integrity."
The government here will make a final decision in December on whether to proceed with a trial.
Associate Local Government minister Louise Upston said New Zealand had learned from the mistakes made overseas.
"Nothing can be 100 percent safe, which is why we're doing a trial in the first place. We'll do a trial, see if there are any issues, and then you have the ability to say, 'well no, it's still too risky' or 'we've managed to cover off the risk, so we'll proceed further'."
So far councils in Palmerston North, Porirua, Whanganui, Rotorua and Matamata Piako have signed up for the trial.
Christchurch City Council will vote this Thursday on whether it will take part.