The Labour Party has lodged a privileges complaint against Conservation Minister Nick Smith for allegedly misleading Parliament.
Dr Smith has repeatedly told Parliament he didn't know about the draft submission from the Department of Conservation on the proposed Ruataniwha Dam until it was reported in September by Radio New Zealand News.
The draft submission said the Hawke's Bay dam project could harm the rivers involved and was substantially different from the final one that was submitted.
Labour leader David Cunliffe says responses to written questions raise doubts over Dr Smith's continued assertions he didn't know about the draft submission before September.
He says Dr Smith's weekly report dated 20 May discussed the content of DoC's submission and referred specifically to concerns about monitoring nitrogen and phosphate levels in the Tukituki River.
Mr Cunliffe says Dr Smith should be sacked as a minister if he is found to have misled Parliament.