South Island mayors will unite to fight the economic pulling power of Auckland's new Super City - a move that may hamper multi-billion-dollar dreams to unclog the city's roads.

Mayors from the lower South Island said yesterday co-operation would ensure their region's voice to the Government was not drowned out by the huge Auckland Council.

Christchurch mayor Bob Parker said a comprehensive South Island grouping was needed in response "to ensure our voice is clearly heard in central Government".

The Auckland Council would be a "huge economic machine".

Its economic development budget alone - used in part to promote the city - was likely to exceed $40 million, he said.

Mr Parker believed the South Island should follow suit, initially by combining tourism agencies - and their budgets - to promote the entire South Island, rather than its individual regions.

The new Auckland Council comes into existence on November 1, replacing eight councils with one representing more than 1.3 million people.

Super City mayor-elect Len Brown has already said his strong mandate meant the Government should listen, and that the rest of New Zealand should help pay for a new city-wide rapid transit system in Auckland.

He has campaigned on three rail project plans - a central city tunnel, a city-airport link and a city-Albany link - which will cost up to $4.75 billion.

Mr Brown could not be contacted last night, but on Monday he told the Herald the Government wanted Auckland to turn itself into "much more of an economic powerhouse" and transport and fixing congestion were important parts of that.

Prime Minister John Key has been cautious about Mr Brown's goals, saying "there is no free lunch when it comes to any of this stuff" and indicating that ratepayers would have to pay.

"The Government is spending $5 billion in Auckland. We're spending $1.6 billion on rail and that's a considerable contribution already," said Mr Key.

New Super City councillor Christine Fletcher - a former Auckland mayor - said last night she was saddened the South Island mayors felt the need to compete.

"It would be foolish to ignore the fact that so many New Zealanders live in Auckland. To neglect the needs of these New Zealanders would not make good business sense.

"It's important for the rest of New Zealand that Auckland succeeds. It's for everyone's advantage."

She did not see the need to compete.

"A lot of South Islanders recognise the needs of the new Super City and that it needs to work, but it shouldn't be at the expense of the South Islanders."

Mr Parker raised the idea of a combined South Island mayoral forum before last year's Local Government New Zealand meeting in Christchurch, and he won support yesterday from Waitaki District mayor Alex Familton and Invercargill mayor Tim Shadbolt.

Mr Familton said change was inevitable and the South Island needed to "speak with one voice".

Mr Shadbolt believed a new South Island grouping would be "great".

Dunedin's new mayor-elect Dave Cull also backed greater regional co-operation, pointing to the possible centralisation of neurosurgery in Christchurch as one example of what the Auckland Super City could possibly lead to.

- Otago Daily Times