Auckland's two mayoral frontrunners went head to head with each other - and Checkpoint's Lisa Owen - in tonight's first mayoral debate hosted by RNZ.

Photo: RNZ / Matthew Hutching.

During the debate, mayoral hopeful John Tamihere accused the mayor, Phil Goff, of sitting on his hands for three years, while Mr Goff accused his opponent of Trumpism in a feisty debate.

The pair traded blows, covering everything from social housing to transport to who's going to charge the most rates.

Mr Tamihere said Mr Goff was a sell out to Wellington who'd introduced stealth taxes in the form of the targeted water and environment rates, and the Auckland petrol tax.

Mr Tamihere said he would ditch those taxes but would get extra revenue from selling 49 percent of the council owned water company Watercare, suggesting the ACC or NZ Super fund would be interested in purchasing them.

Mr Goff said that was "bull****" and accused Mr Tamihere of making statements like US President Donald Trump.

He said selling Watercare would mean every household would have to pay up to $300 more a week - the equivalent of a rate rise of up to 12 percent.

The 18-lane train, walking and driving Harbour Bridge promised by Mr Tamihere was slammed by Mr Goff, who said trains wouldn't even be able to make it up and the costs would be sky high.

But it was Mr Tamihere's turn to accuse Mr Goff of telling "porkies," saying the costs were all achievable.

Turning to social housing, he said poor people deserved places to live and that was why he was fighting for more affordable and social housing in major city developments.

Mr Goff countered they had the ratio right.

Mr Tamihere finally answered questions on past comments he had made that gay sex was "unhealthy and violating" saying he no longer held that view.

He has previously tended to avoid answering the question directly, making only vague allusions to the fact he had changed.

Ahead of the debate, the pair had expressed little love for each other so far.

Mr Goff argues he's a steady pair of hands and is bringing better public transport and cleaner water to Auckland.

But Mr Tamihere says it's time for some colour, for someone to stand up and champion issues like his proposed 18-lane Auckland Harbour Bridge.

You can watch the whole debate below.