Councillors at yesterday's full council meeting voted unanimously, and without debate, to join the South Island Strategic Alliance (SISA).
The grouping of up to 27 South Island councils had been discussed since last year, and in recent weeks endorsed by the Otago Regional Council, and Central Otago and Clutha District Councils.
A report to yesterday's council meeting in Dunedin said the "coalition of the willing" would help promote a "South Island voice", including when talking to the Government in Wellington.
Dunedin Mayor Dave Cull told Radio New Zealand the alliance helps give the South Island a collective voice which isn't fragmented when dealing with central government.
"It's a recognition that right across the South Island we have some common interests and it is looking for ways to cooperate in areas of mutual benefit, it might be shared services, it might be shared contracts for say road maintenance, and also to have a united South Island voice vis-a-vis central government."
Invercargill City Council is to vote whether to join the alliance soon, Mayor Tim Shadbolt told Radio NZ. He said the Auckland Super City has put the country "out of kilter", as its needs are out of control.
"We're just seeing this phenomenal growth continuing to spiral out of control, and the demands that are going to be made on motorways and other developments in Auckland to the detriment of the South Island is a real wake-up call."
- with nzherald.co.nz