The ancient Pukaki crater near Mangere will become a public reserve after being bought for $6.07 million by the Manukau City Council.

The council approved the purchase last Thursday.

It will own 25ha of land around the lagoon explosion crater rim and the leasehold interest in perpetuity of 36ha of flat land inside it.

The crater, which is between 80,000 and 100,000 years old, is one of Auckland's oldest and least modified volcanic craters.

The council aims to create a 'premier park containing estuary coastline and dramatic volcanic landforms as well as significant natural and cultural features'.

The public won't be able to use the new park immediately because the vendor John Prangley can graze stock there for another 12 months while the council plans for its development.

Mayor Sir Barry Curtis says co-management for the new reserve will be negotiated with the Pukaki Maori Marae Committee, who own the freehold title to the crater floor.

He believes the new park will become one of Manukau's most significant open spaces.

"This was one of the only opportunities for a largely unmodified explosion crater to come into council ownership," Sir Barry says.

"Preservation of sites with significant natural, cultural and recreational values is a vital component of a young and rapidly growing city such as Manukau."

Bayleys Manukau, the real estate agency that marketed the property, reported the tender attracted strong interest from developers who could have turned the land into rural lifestyle blocks, Sir Barry says.

Te Akitai o Waiohua are mana whenua of the area, based at Pukaki.

Marae committee spokeswoman Maahia Takaanini-Wilson says Te Akitai Waiohua are delighted with news of the purchase of the Pukaki land, which was the site of an ancestral pa.

"Not only does the purchase continue the council?s acknowledgement of the 1985 Waitangi Tribunal decision on the Manukau claim, it also recognises the perseverance and commitment of tangata whenua, Te Akitai Waiohua and Tainui, to protecting historic sites," she says.

The land also has important associations with the Waiohua people as the site of urupa, or burial grounds, and papakainga, or villages.

Te Pukaki Tapu o Poutukeka, the sacred wellspring of Poutukeka, is the name given to Pukaki crater by tang-ata whenua. Poutukeka was one of the crew of the Tainui waka and the original ancestor of all 33 generations of mana whenua in the area.

In March, Mr Prangley was reported in the Manukau Courier as saying his family considered itself a joint custodian with the marae committee of one of Auckland?s most valuable assets.

He said then the ideal buyer would be a private owner who respected the history of the land or a public body like the city council or the regional council, which could work with the marae committee to convert it into a public park.

The money for the purchase came from the council's cash-in-lieu of reserves account, which contains money paid by developers to the council in lieu of land being provided for reserves on private sector subdivisions.

Money from that account can only be spent on buying land for public open space, active or passive recreation or development of land for this.