National's claiming South Island water assets are set to be co-owned by Ngai Tahu.

Party leader Judith Collins says the Government is proposing to transfer 50-per cent of publicly-owned water assets, to the iwi.

It's the latest in a series of questions raised by the Opposition Leader, over Labour's interpretation of honouring the Treaty.

Collins says the plan was presented to 23 mayors, and would consolidate all water infrastructure in the South Island into one organisation.

She says mayors have told her, that local councils who have purchased infrastructure through ratepayers, would get no compensation for this.

However, Ngai Tahu is rubbishing the claims. 

Chair of the Ngai Tahu freshwater group Dr Te Maire Tau says it's deceptive and wrong.

He says if Collins had bothered to ask them about the proposal instead of seeking headlines, she would have had the facts sooner.

Tau says the tribe hasn't called for ownership of the assets.

Listen above as Judith Collins discusses the latest claims with The Weekend Collective