Whanganui has been given four weeks to get rid of the foul stench that has seen the city dubbed "Ponganui" for the past month.
Horizons Regional Council yesterday issued Wanganui District Council an abatement notice, ordering it to stop emitting an objectionable odour beyond the boundary of its wastewater treatment plant by February 9.
If it does not, enforcement action may be taken, which could range from fines through to the plant being shut down.
The stench has been caused by recent dumps of trade waste - including fat, proteins and sulphide - beyond what the consents of local businesses allow.
It is not known which company is responsible, but mayor Annette Main said she had written to the six that have consents to let them know any more excess dumps would not be tolerated.
She believed the treatment plant could be compliant within four weeks.
"We're going to have to . . . the consequences of course will be dire because we can't stop running the plant."
The council would also look at what could be done to ensure the plant worked properly in the years to come, as it was clear it had not been since it opened in 2007, she said.
Horizons spokesman Nic Peet said the regional council was obligated to act on the stench after it also received a large number of complaints.
- The Dominion Post