Department of Conservation staff in Whangārei have been forced to climb fences to visit its reserves to investigate complaints that Northpower is blocking public access to them.
The power company has installed locked gates to keep people away from the 100-year-old Wairua Falls Hydro Power Plant, citing safety reasons.
Fish and Game said it made it hard for people to get to the reserves.
Northland's rivers campaigner Millan Ruka said he could no longer launch his boat or kayak from the power station site to carry out river patrols.
Both have opposed Northpower's application to renew its resource consent for the station.
DOC's Whangārei manager Louisa Gritt went to investigate the problem yesterday and confirmed it was now difficult to access reserves.
"We had to clamber over and under fences, using a paper road, so it's not easy to get to. Certainly it's not ideal."
Ms Gritt said her next step was to meet with Northpower.
"Just to understand what their issues are over the gates and what concerns they have about allowing access through there."
The company had a right to deny entry to the power station land and if DOC could not resolve the problem with it might look at improving alternative access, Ms Gritt said.
Millan Ruka, who accompanied Ms Gritt on what was her first visit to the Wairua reserves, said he was disappointed to see a herd of cattle, including a large bull, grazing the conservation land.
"The only way those cattle could have got onto that DOC reserve was through the Northpower gates," he said.
Northpower did not return RNZ's requests for comment.