She referred to a previous poll on kerbside recycling that resulted in no change, and left people feeling they were not listened to.
"We are going into the 2022 election with 12 elected members, which is not what people told us in this poll," she said.
But deputy mayor Jenny Duncan said a reduction to 10 councillors wouldn't save ratepayers money because the same salary pool would then be split between the 10.
If the council wanted to do that, it would have to do some major consultation.
"It will cost a lot more than any financial savings. I highly don't recommend that," she said.
Twelve councillors means more new faces and more diversity, Cr James Barron said.
And Cr Josh Chandulal-Mackay said it made it easier for new entrants to get elected.
McDouall said he has sat on two councils with inactive members and knew that they could work very effectively with 10. He made a campaign commitment in 2016 to investigate dropping the number to 10.
"I was behind putting it to the referendum, and I think we patronise voters at our own peril," he said.
Another non-binding poll asked whether councillors should be elected by ward, or across the whole district. Most, 10,373, preferred the "at large" system and 2327 would prefer voting by ward.
Chandulal-Mackay said the "at large" option was more democratic.
"It allows people to have a say on the whole composition of council."
Councillors agreed to stick with "at large" voting and the first-past-the-post voting system.
In the binding poll 10,608 preferred that. Only 2590 wanted to try the single transferable vote system.
The next review of local government voting in Whanganui is due in 2024.