Hawke's Bay Regional Council (HBRC) says a "clear plan" is needed from the Central Hawke's Bay District Council (CHBDC) on how it intends to modify its wastewater plant to meet stricter standards.
A HBRC council report this month raised "serious concerns" with the new $6 million wastewater plant in Central Hawke's Bay.
The study showed despite a recent upgrade that harmful bacteria and wastewater were being released into the Tukituki River at unacceptable levels.
Central Hawke's Bay District Council decided to construct floating wetlands to meet new treatment standards.
Wetlands were constructed last year at Waipawa in July and in Waipukurau in September. The new system also used screening of the influent, biological attachment surfaces curtains and aeration, dosing with aluminium sulphate, and ultraviolet irradiation.
HBRC group manager resource management Iain Maxwell said his council did not play any part in the final selection of the wastewater treatment option or its design, and its role was now to ensure CHBDC met the required standards.
He said it was too early to know whether a full prosecution against CHBDC was warranted.
"What I am interested in is seeing a positive outcome and meeting those new standards, taking court action against them at this point in time will not achieve that."
Meeting the new discharge standards was a "non-negotiable bottom line" and HBRC would "continue to closely monitor the situation to ensure a process is in place to achieve that".
In response, CHBDC chief executive John Freeman said his council had "a plan of attack," and was waiting for the final report.
"We've got a plan we're putting in place, and the plan is to get [HBRC] down at the end of next week to show them what we're doing and what we intend to do."