Monitoring found that degradation of the river was mild upstream from the outlet point, and severe downstream.
Palmerston North Mayor Jono Naylor has told Horizons chairman Bruce Gordon he wants a chance to respond to the report before it is debated by the committee.
The committee thought that was a fair request, chief executive Michael McCartney said.
The report has now been tabled until October 11, when it will be discussed.
Interest in the health of the Manawatu River is high. Palmerston North City Council signed up to the Manawatu River Accord earlier this year, making a commitment to comply 100 per cent with its resource consent conditions.
The accord's vision statement is: "If the water is healthy, the land and the people are nourished."
Horizons has several possible actions open to it.
It can issue an abatement notice to the council, requiring it to cease the damaging discharges.
It can also review the conditions of the consent and it can initiate a joint working party to get improvement.
The council received a qualified approval of its freshwater management in a report from the Auditor-General presented to Parliament yesterday.
It was one of four regional councils audited on land and water management.
The report said it was maintaining and enhancing water quality in the Whanganui and Rangitikei river catchments, but not the Manawatu River catchment.
Its programmes should support future improvements in the quality of the region's freshwater.
Mr McCartney said while the council was not quite there for the Manawatu, the report acknowledged it was on the right path to getting there.
The report commended several of its programmes, including the Sustainable Land Use Initiative (SLUI) and online tools such as WaterMatters.
There were still improvements the council could make, he said, and it would review the recommendations and address any gaps.