Hawke's Bay Regional Council chairman Fenton Wilson is demanding fellow councillor Tom Belford formally declare his interest in a lobby group opposed to the Ruataniwha dam.
But Mr Belford says such a declaration would be inconsistent with the approach taken by other councillors and while he is sceptical about the Ruataniwha project, he remains open-minded ahead of a crucial vote next month that could seal the fate of the $275 million scheme.
Mr Belford is a founding member of Transparent Hawke's Bay, an advocacy group pushing "open processes, reliable information, and public involvement in councils' decision-making".
It lodged a submission opposing the irrigation scheme with the board of inquiry convened to assess resource consent issues related to the project and Mr Belford spoke to the group's submission in January during the board's hearing process.
When a conflict of interest register was circulated for updating at a meeting of the council on Wednesday, Mr Wilson challenged Mr Belford to record his involvement in Transparent Hawke's Bay.