Conservation Minister Nick Smith appears to be at odds with his departmental experts about the science behind the Ruataniwha Dam.

A leaked email from the deputy director of conservation says Dr Smith had some concerns about the draft DoC submission to the Board of Inquiry into the Hawke's Bay dam and wanted to see it.

The concerns raised in the draft submission by senior DoC experts leaked to Radio New Zealand are that the nutrient management model produced in a laboratory by NIWA is untested and risky and could kill the Tukituki river.

However, Dr Smith told Morning Report that experts such as NIWA are involved in the process to make sure there is a really good quality decision out of the Board of Inquiry.

He says former director general Al Morrison also told him NIWA is the best expert body on nutrient management and is extensively involved in the issue.

The email leaked to Radio New Zealand was circulated to senior Department of Conservation staff, including the director general, and says Dr Smith wanted to see DoC's submission before it was lodged with the Board of Inquiry.

The board is considering the resource consents for the Hawke's Bay Regional Council's proposed Ruataniwha water scheme and its associated "Plan Change 6".

Dr Smith said in Parliament on Tuesday he did not have access to the draft submission until he heard it on Radio New Zealand National on Tuesday morning.

He told Morning Report on Thursday he did not mislead Parliament.

The leaked email is dated 29 July at 6pm and was from Doris Johnston, the Department of Conservation's deputy director-general, policy and regulatory services.

There were four recipients. One was then DoC director general Al Morrison and the three others were senior DoC planning managers.

The email said:

Hello,

The minister wants to see the submission we are proposing to make on the Ruataniwha before it is lodged.

I suggest you send it over tomorrow for him to consider the draft and also attach the briefing note you provided me.

I am in Hamilton tomorrow but back on Wednesday. He is concerned and is likely to query whether we leave it all to the EPA to consider.

Minister's comments in Parliament

Dr Smith told Parliament during question time on Tuesday he had not had access to the draft submission.

"I raise a point of order, Mr Speaker. The member has claimed in the question that I had access to a report that I did not do so, until I heard it on Radio New Zealand National this morning."

Once he emerged from the House he told reporters, "I did not know that this draft document even existed until this morning. And to have accusations that somehow I have covered up its existence - it is somewhat difficult to cover something up when you didn't even know it existed."

Dr Smith told Morning Report on Thursday an initial 50 page report was written by junior staff, and senior DoC staff voiced concerns in late July that it went beyond the department's brief.

He says it is entirely reasonable for him to ask the department for more information after conflict within DoC over the submission.

Radio New Zealand understands DoC prepared only one draft submission.

Radio New Zealand sources said it was common knowledge inside and outside DoC that on Monday 29 July Doris Johnston met with the minister.

It was following that meeting, and later that day, that Ms Johnston sent the email. Sources say the decision not to submit the draft submission was conveyed to staff on the morning of Wednesday 31 July.

However, Ms Johnston released a statement on Thursday saying Dr Smith never saw the early draft of DoC's submission and did not give direction on it.

She says the decision not to lodge the draft submission with the Environmental Protection Agency was made based on the conservation values of the Tukituki Catchment, which did not justify the resource investment required to make a detailed submission.

Ms Johnston says the decision was made after considering all internal advice and the minister was informed about the process in the standard way.

Radio New Zealand sources say DoC staff and external advisors were devastated that the draft would be not submitted and that the final submission was just two paragraphs and "neutral".

Submission details

The draft submission on the Ruataniwha Dam project said the Hawke's Bay Regional Council proposal was an "untested" and "risky" approach to water management that could kill the rivers involved.

The submission leaked to Radio New Zealand said the council's approach to managing toxins from intensive agriculture associated with the dam might not be sufficient to support life in rivers.

It also said the ability to reverse the toxicity would be limited.

The submission said the risks of the dam project had not been fully assessed, with an inadequate management plan for potentially high impact effects on rivers.