Over 450 Moriori from as far away as Australia have descended on the Chatham Islands to celebrate today's opening of the first ever Moriori marae - the heart of a cultural renaissance.

For about 80 per cent of them it is the first time they have ever set foot on the islands, about 800km east of Christchurch.

Prime Minister Helen Clark is among those attending the opening of the $4 million Kopinga Marae - named after the kopi groves Moriori traditionally used as a gathering place.

The ceremony includes the unveiling of the meeting house's central poutokomanawa - a post of the heart - on which the names of all the Moriori recorded on the 1835 Census are inscribed.

This will be followed by a renewal of a 500-year-old covenant known as Nunuku's law of non-violence - which forbade bloody conflict - last renewed in the same year - 1835.

That was the year the islands were invaded by two Taranaki iwi, and the decision to uphold the covenant helped result in the decimation of the Moriori population.

In the ensuing years Moriori were the subject of many erroneous myths and considered to have "died out".

Twenty years ago historian Michael King, together with descendants of the original inhabitants, began challenging those myths, sparking the renaissance and encouraging others to acknowledge their Moriori heritage.

In 2001 the Waitangi Tribunal found Moriori were a unique Maori tribe who settled the main island in the group - Rekohu or Chatham Island - between 600 and 800 years ago.

It found they were entitled to compensation from the Crown for its failure to protect them from the brutal enslavement imposed on them by the Taranaki iwi.

The marae was built by the Hokotehi Moriori Trust and trustee Nick Preece said yesterday it would be a focal point for the development of the Moriori language and culture.

It would also be used to disseminate Nunuku's law, he said.