But it got an hour's discussion at most. Councillors had a range of views, and agreed to leave the policy open.
That leaves local authorities free to ask for help to fund district projects that have regional appeal, and councillors free to consider them on their merits. It also means the council response may disappoint the region's mayors.
A definition of core business came up this week because Horizons has been asked for more funding towards government's Manawatu-Whanganui economic development plan, Accelerate25. The funding would be for a full-time staff member.
Horizons has already put in $230,000, with half from reserves and half from rates. And it is contributing the time of chief executive Michael McCartney and strategy and policy manager Nic Peet.
Regional economic development should rest with central government, and not Horizons, Mr Cotton said.
"While Michael and Nic are away dealing with those issues, they can't be concentrating on the One Plan."
Getting intensive farming consenting right under the One Plan is also essential for economic growth, he said. It was the main item for Tuesday's meeting.
"Farmers are in no man's land. They can't invest with this uncertainty."
Resolving the consent matter would also ensure farmers aren't "running illegal operations".
Like most of his fellow councillors, Mr Cotton wants a resource consent pathway that "works towards better water quality and doesn't put people out of business".
Whanganui's other Horizons councillor, Nicola Patrick, agrees the council's core business needs to be defined.
She was disappointed nothing was resolved at Tuesday's meeting.