Labour has slammed the lack of transparency around the "mystery" investor in the Ruataniwha dam.
This reaction came from Labour's Local Government spokeswoman Meka Whaitiri after ACC again refused to either confirm or deny its involvement in the scheme - this time via an Official Information Act request.
Earlier this year, Hawke's Bay Today reported that there was speculation around the fund being a potential investor in the dam.
When approached about this, ACC said it was unable to comment on any projects the Crown entity may be currently looking into.
Yesterday the fund echoed these words, after it declined the request from RNZ News that sought information it held regarding its possible investment in the Hawke's Bay dam.
ACC responded to the latest request, saying its position would be prejudiced if it disclosed whether the information asked for even existed.
"ACC neither confirms nor denies the existence or non-existence of the information," it said.
However, Ikaroa-Rawhiti MP Ms Whaitiri said, as a Crown organisation, ACC should be transparent with New Zealanders and state whether it is investing in the dam.
"Hawke's Bay ratepayers are fed up with the endless speculation over the 'mystery investor' in the dam," she said.
"Millions of dollars of public money has already been spent on Ruataniwha and Kiwis deserve to know if even more is about to be sunk into this white elephant," Ms Whaitiri said.
She said it was also concerning that ACC Minister Nikki Kaye was not aware of whether or not the fund was planning such a significant investment.
A spokesman from Ms Kaye's office said Ms Whaitiri needs to understand that, under the Crown Entities Act, the minister has no involvement in the decision making process for ACC investments.
"The responsibility for managing ACC investment funds resides with the ACC Board."
Meanwhile, the Green Party is calling on ACC not to invest public money into the dam, saying it could be a disaster for the Hawke's Bay environment.
"The case for the Ruataniwha dam doesn't stack up economically or environmentally, and ACC shouldn't pour New Zealanders' money into it when even private investors won't," Green Party water spokeswoman Catherine Delahunty said.
As it stands, the dam scheme has failed to attract any publicly known private investors, with Ms Delahunty saying it could end up relying on fully on public funding.
"ACC should be using its investment power to help clean up our rivers, not contribute to their decline by funding projects like the Ruataniwha dam."