The Department of Conservation is accused of making secret deals with a power company over plans to build a 72-megawatt hydropower scheme on the Wairau River in Marlborough.
Trustpower was granted resource consent for the project in August last year.
The department is part of an Environment Court appeal against the $280 million project, but now says it is close to reaching an agreement with TrustPower.
The department says it has been open about its discussions with TrustPower and hopes the parties will agree to conditions which will resolve DoC's worries about the plans before the court hearing.
But the Save the Wairau group says DoC's actions are not transparent, while Fish & Game says DoC has been in confidential negotiations with TrustPower.
DoC says any agreement will be made public through the Environment Court hearing.
The department had concerns regarding the bird population of the river.
TrustPower says the discussions have not included an offer of a payout.