The decision puts the Otago Regional Council (ORC) in line with the Dunedin City Council, the only one of Otago’s five territorial authorities to use the electoral system where voters rank their preferred candidates.
Cr Kate Wilson, of the ORC’s Dunedin constituency, said she had always supported STV.
The proportional-representation system would have the biggest impact in Dunedin, where six councillors were elected.
"It really isn’t a huge change in those other constituencies, but the merit and the benefit will be ... in Dunedin, where those people are already attuned to it.
"It equalises everyone’s voting ability throughout Otago."
STV tended to promote representation more reflective of the makeup of communities, Dunedin councillor Cr Alan Somerville said.
Cr Bryan Scott, also of the Dunedin constituency, said the council had a responsibility to encourage people to stand to become councillors and STV promoted minority candidates.
Another Dunedin councillor, Cr Tim Mepham, supported the switch on the basis of the work that had been done by the future of local government review, which recommended STV for all councils.
On the other hand, Cr Michael Laws, a Dunstan councillor, called it "rude" to impose the change on Waitaki, Central Otago, Queenstown Lakes, and Clutha voters, who in local elections used first past the post.
"This is an arbitrary judgement that 11 elected people will be making around this table now and imposing upon people who have not clamoured for reform.
"The farmers, the residents of Cromwell and Alexandra, Queenstown and Wanaka, are not beating a path to the Otago Regional Council’s door saying, ‘for God’s sake make things better, change the electoral system’.
"Their needs are a lot more prosaic, realistic and common sense than that.
"It appears, from somebody who doesn’t live in Dunedin, that this is yet again another one of those impositions of Dunedin values on the Otago region."
The council considered the issue three years ago when councillors decided to retain first past the post for last year’s election, but also hold a public poll on the matter alongside the vote.
Several months before voters went to the polls, though, councillors dropped the poll because of the work being done on the issue by the future for local government review panel.
Councillors considered the issue again in June this year and resolved to examine the issue in a closed-door workshop on electoral systems as well as consult Otago’s local councils.
Only Crs Laws, Gary Kelliher and Kevin Malcolm voted against the change at Wednesday’s meeting.
Cr Lloyd McCall abstained.
Cr Andrew Noone was absent for the vote.
The council must now, by September 19, give public notice of the decision and the right of electors to demand a poll on the electoral system to be used at the next two elections in 2025 and 2028.
