A former mayor has hit out at a proposal to outsource Rotorua's wastewater management, one in a chorus of opposition to the idea.

Kevin Winters was mayor of Rotorua from 2004 until 2013, when he was beaten by incumbent mayor Steve Chadwick.

On Thursday, he made a submission on Rotorua Lakes Council's proposal ‘Sewerage and Sewage: establishing a stable, reliable and safe network'.

The document proposes the council enter into a contract with a consortium of Trility, Fulton Hogan and Stantec for the provision of wastewater services across the district.

Trility is owned by Hong Kong-based investment holding company Beijing Enterprises Water Group, having acquired it in 2018.

'I come to you with a heavy heart,” Winters began his submission, emphasising he was submitting as a private individual, not as a Bay of Plenty Regional councillor.

'Since 2013 I have stayed away from this organisation in terms of my opinion but there's some things I just cannot let go.

'I feel very strongly about this.”

He said the statement of proposal was 'really biased” in favour of the council's preferred option to enter into a 10-year contract with Trility.

'There's an unconscious bias in this report to steer you to option one.”

Winters said there were 'far too many risks and far too many unanswered questions” with the proposal.

'Quite frankly it's horribly the wrong decision.

'This can be done in-house. This is your core business.”

Sitting councillor Reynold Macpherson also submitted on the proposal, sparking controversy about predetermination.

Speaking in opposition to it, he laid out nine issues with the proposal, including self-reliance for core infrastructure, undermining progress and impacts on accountability from outsourcing.

Much of his commentary quoted other people.

Out of 12 submitters at the hearing, just one was in favour of the partnership with the Trility consortium - submitter John Pakes.

'The task before you is challenging. It is a challenge you must meet,” Pakes said.

'You should bite the bullet and get on with it."