A hui in Christchurch has been told the Foreshore & Seabed Act 2004 should be repealed.
A panel is hearing submissions at a series of hui and public meetings as part of a Government review of the act.
Speaking on behalf of Ngai Tahu, Tim Rochford told the panel on Tuesday that the act is the most significant attack on Maori property rights in his lifetime.
He also said it was a stain on the conscience of the nation.
The panel will continue to hear submissions in April and May and will report to the Government by the end of June.
The Labour Party, which introduced the Foreshore and Seabed Act, says it should be changed to allow Maori to apply to the courts for customary title.
The 2004 Act prevented Maori seeking customary title, and vested ownership of the foreshore and seabed with the Crown.
But in its submission to the Ministerial review of the law, Labour has altered that position, while arguing that the current rules around access and usage rights should remain.
The Act's architect and retiring Labour MP Michael Cullen says customary title would be hard to establish, and apply largely to remote areas - and it could not be converted to a freehold title.
He says customary title would give iwi and hapu enhanced standing under the Resource Management Act, and recognition of customary usage rights.