The next step in iwi battles against the Government's Kermadec Marine Sanctuary proposal is set to hit the courts today.

The plan sparked vociferous iwi protest last year, on the grounds it breaches the 1992 fisheries settlement.

Two iwi, Te Whanau a Apanui and Ngati Mutunga o Wharekauri, are taking a legal challenge against the Crown.

The Government's trying to have the case stopped on the basis it interferes with the privilege of Parliament to set legislation.

A preliminary hearing on the case is due to be heard at the High Court in Wellington today.