The landowner at the centre of the Ruataniwha Dam project says environmental groups wanting access to the property are being ignorant and arrogant.

The Environmental Defence Society, along with the Royal Forest & Bird Protection Society of New Zealand and Fish & Game, claims its researchers have been refused access to the site, and says it will be filing a legal complaint with the Board of Inquiry.

Landowner Craig Preston told Morning Report he made it clear in July that due to farming commitments, he would not allow access until 10 October.

He said that unless he gets an apology from the groups, he may exercise his right to deny them access even after that deadline.

The Environmental Defence Society says it is to lay a complaint with the Board of Inquiry because its researchers have been refused access to the Ruataniwha dam site.

Hawke's Bay Regional Council says access to the site is a matter for the landowner.

But EDS chair Gary Taylor says the council does not seem to be cooperating and seems to be putting up obstacles.

Hawke's Bay Regional Council member Liz Remmerswaal is calling for a deadline on submissions to be extended.

Cr Remmerswaal says researchers want the same access the council and the board of inquiry have had, so they can look at threats to biodiversity and native species.

The submission process opened in August and ends on 8 October.

Dam details not available to opponent

Fish & Game says Hawke's Bay Regional Council and NIWA are refusing to hand over key evidence for the Ruataniwha dam proposal so it can be independently evaluated.

It has filed legal documents with the Board of Inquiry into the project asking it to force NIWA and the regional council to release the model used to justify its approach to water management.

A leaked Department of Conservation draft submission called the model, known as TRIM, a risky and untested approach and warned it could make the Tukituki River toxic.

NIWA and the regional council say the model is NIWA's intellectual property and will not release it, but will run data through it for Fish & Game.

But Fish & Game says that is like watching the mechanic fix the vehicle rather than getting into the mechanics yourself.

The Transparent Hawke's Bay group says it is concerned NIWA internally peer-reviewed the TRIM model and it has not been subject to independent scrutiny.