A stranger threatened to "put a bullet in" a Hamilton City councillor as emotions ran high during the last round of wrangles over fluoride yesterday.

The man - who was unknown to other anti-fluoride campaigners present - allegedly made the threat to councillor Ewan Wilson as the city council meeting broke for morning tea.

Mr Wilson, who described the incident as evidence of what he called the "lunatic anti-fluoride fringe", has laid a complaint with police.

The man's remarks tainted those with genuine and considered views on the issue of fluoridation, and were evidence that a small group of anti-fluoride activists held extreme views, Mr Wilson said.

The outburst was an extreme example of the issue's polarising nature, with other speakers during the public forum - which precedes council meetings - confining themselves to verbal attacks on Mr Wilson and what they called "biased" media.

The meeting agreed to decide next Friday whether a referendum on water fluoridation will be held at the same time as October's local body elections.

A notice of motion by councillor Dave Macpherson and signed by five city councillors has for the first time cleared council to consider holding a referendum at the same time as the elections.

This would dramatically reduce its potential cost to an expected $12,000.

A petition organised by Mr Wilson calling for a citizens' initiated referendum has easily met the 1500 enrolled city voters needed to force a debate, the council has confirmed.

Because the council voted last year not to hold a referendum on fluoridation, there is a higher threshold for the council to overturn or rescind that decision.

That threshold has now been met, meaning when council considers the 2000-signature petition it will also have the ability to do as it asks.

Whether the numbers are there for that to happen remains unclear, however yesterday's outcome proved the council is at least willing to put it to the vote. The decision followed a string of speakers who crammed the wharenui at Kirikiriroa Marae urging city councillors to stick to its earlier tribunal decision which removed fluoride from the city's treated water supply from June 21.

Ted Niness said the process was "robust, fully informed and dispassionate".

"A referendum is not an appropriate vehicle to deal with this issue unless there is a lot more information provided to the public," argued Mr Niness.

However, petition organiser Selwyn June said Hamiltonians "overwhelmingly want fluoridation". "This is an issue which must go to the wider public," he said.