Marlborough iwi say erosion is threatening a 700-year-old site at the Wairau Bar which they believe is the first Maori settlement in New Zealand.
Archeologists are preparing sites at the Wairau Bar near Blenheim for the return of ancient bones taken for study by Canterbury University more than 60 years ago.
Richard Bradley, of Rangitane, says erosion could ruin the historic site, which could be destroyed within 50 years unless the problem is tackled.
He said the site is as important historically as Waitangi, because it is the likely place where Maori first settled in New Zealand.
Iwi want the area declared a World Heritage Site as a first step to protect it.
The remains of ancestors will be re-buried at the Wairau Bar in April.