Prime Minister John Key had committed himself to working with the Iwi Leaders Group in 2009, and since then the Crown had worked closely with the group to frame policy development and develop drafts of advice to ministers. That work should continue.
"It is likely that a hearing process based on allegations of Treaty breach would not necessarily be productive, and may cut across the engagement and dialogue between Maori and the Crown."
Mr Gough also noted that the Crown still needed to engage Maori on the tribunal's report findings from the Wai 262 claim, which set out a framework for considering resource management issues relevant to the water.
A national water claim would lead to an inquiry "enormous in breadth and complexity" where all iwi and hapu views would need to be heard, Mr Gough said.
"Further, there is no evidence of iwi support for the representative claim.
"Given the significant Maori participation [in water reform process], the tribunal should be assured of widespread support for a national claim of this kind before diverting resources to what would be a substantial inquiry."
That position has some support from the Freshwater Iwi Leaders Group, members of which include Sir Tumu te Heuheu, Tuku Morgan, Mark Solomon, Toby Curtis and Brendon Puketapu from Ngati Tuwharetoa, Tainui, Ngai Tahu, Te Arawa and Whanganui respectively.