Former Christchurch Mayor Garry Moore denies his comments in two interviews were defamatory.

A top council manager alleges former Christchurch Mayor Garry Moore has defamed him in comments regarding the city's water chlorination and is seeking $500,000 in damages.

Christchurch City Council head of three waters and waste John Mackie claims Moore defamed him by suggesting he was pushing the interests of pro-chlorination group Water New Zealand, in papers filed to the Christchurch High Court.

Moore denies either making the comments, or that they amounted to defamation.

JOHN KIRK-ANDERSON/STUFF Council three waters and waste head John Mackie, at the Christchurch City Council meeting where it was voted the the city's water be chlorinated. To his left is Canterbury medical officer of health Dr Alistair Humphrey.

The claims centre around an article containing quotes attributed to Moore, published by Newsroom, and similar allegations made by Moore in an interview with Newstalk ZB's Chris Lynch.

READ MORE: The South Island towns (and city) fighting chlorination

Mackie claims Moore's comments implied he was "dishonest and unethical", both of which were "untrue and defamatory". Mackie is seeking $180,000 in damages for the Newsroom article and $330,000 for Moore's Newstalk ZB interview.

In his statement of defence, released by the High Court on Monday, Moore denied his comments were defamatory, but if they were he was expressing his honest and genuine opinion. He also says the subject matter of his comments was a matter of public concern responsibly communicated.

The stoush centres on the city council's controversial decision in January to chlorinate Christchurch's drinking water for up to 12 months while it repaired well heads, which were deemed unsafe and vulnerable to pollution from dirty surface groundwater.

Mackie was elected to Water NZ's board last September after a longstanding association with the organisation stretching back more than 30 years, according to its website.

He joined the Christchurch City Council in 2013 after an engineering career in Wellington, Auckland and Dunedin. In February, he was nominated for New Zealander of the Year and for the Local Hero Award for service to the preservation of safe drinking water in New Zealand.

Moore was Christchurch mayor between 1998 and 2007. In June 2017 he was appointed as chairman of the Mayor's External Advisory Group, set up to provide advice on the council's long-term capital works programme.

Council chief executive Karleen Edwards said she did not know of any of the details relating to the case.

She said employees of most councils – if not all – had members on Water NZ.

"Councils have benefited from membership historically – particularly through the sharing of information, both informally and through conferences, meetings and publications."

She said Mackie, who was at work as normal, did not get paid for his role on the Water NZ board.

However, Christchurch Mayor Lianne Dalziel said she wanted the council to review its membership of Water NZ, because of the advocacy stance the group had taken.

She said she could not express a view on the defamation case and had not discussed the issue with Moore.

Water NZ has been campaigning for permanent chlorination in Christchurch and across New Zealand. It is a non-profit organisation, representing 1900 water treatment specialists across New Zealand, including water treatment companies.

No date has yet been set for the hearing.