Wanganui District Council will sue engineering consultants MWH over failures at the council's wastewater treatment plant.
Mayor Annette Main yesterday confirmed that the council will file court proceedings against MWH by the end of August.
The decision was made by councillors at a closed session of an extraordinary council meeting on Monday.
The Wanganui Chronicle understands the decision was unanimous, although at least one councillor - Clive Solomon - had given his apologies for the meeting.
The proceedings relate to MWH's involvement in the concept and final designs of the district's malfunctioning wastewater treatment plant.