A Far North iwi claiming customary title over surfing mecca Shipwreck Bay and part of the Ninety Mile Beach says free public access will not be restricted.

The assurances have been echoed by Attorney-General Chris Finlayson but branded "totally glib" by Far North Mayor Wayne Brown.

Northland's Te Rarawa and the Coromandel's Ngati Porou Ki Hauraki are the first iwi to formally seek customary title under the new Marine and Coastal Area Act - the law that this year replaced the controversial Foreshore and Seabed Act.

Te Rarawa chairman Haami Piripi said the iwi was expected to seek customary title to all the coastline in its rohe (tribal area), which includes Ninety Mile Beach from Hukatere south, the Whangape and Herekino harbours, and North Hokianga.

To gain customary title, iwi must prove exclusive and continual use of the foreshore since 1840 without substantial interruption, and Piripi said Te Rarawa was in a strong position.

"Because we are wild west coasters, we have tended to stay on our land and have not had the same wave of colonisation as other areas," he said. "On much of our coastline, up to 90 per cent of the population is Maori."

Once granted, customary marine title areas other than specified wahi tapu that require protection would be subject to the right of free public access for activities including surfing, fishing, swimming and boating.

The tribe had been "hammered" last year when it took the Far North District Council to the Environment Court over sewage discharged into the Hokianga Harbour, Piripi said.

Customary title would give Te Rarawa more clout to deal with pollution and issues such as paua poaching.

Yesterday, when asked if he thought Shipwreck Bay would remain a top surfing location if Te Rarawa gained customary title, Brown - a veteran surfer - said no one was sure what the law permitted under the new act. "I don't know what will come out of this," Brown said. "I think the minister is completely unbelievable."