Plans for an Auckland stadium descended into farce yesterday after nearly half the city council went behind the Mayor's back to petition the Prime Minister to reconsider Carlaw Park as a possible site.

Mayor Dick Hubbard said his "jaw hit the floor" when he learned that nine of the city's 20 councillors had signed a letter this week urging Helen Clark to consider the derelict former rugby league ground - instead of a national waterfront stadium or a revamped Eden Park.

The Herald on Sunday broke the news to a stunned Hubbard yesterday afternoon. He said the council had already voted to back the waterfront stadium in principle last month.

"I must admit my first reaction is that I'm a little surprised," he said.

However, he rejected the suggestion that the rebel action jeopardised Auckland's chance of hosting the Rugby World Cup.

Sports Minister Trevor Mallard has insisted Auckland local authorities must reach a unanimous decision on the waterfront versus Eden Park by November 24 - or lose its status as the main cup venue to Christchurch.

"No, Auckland will get its act together in two weeks," Hubbard said.

Yesterday Mallard reiterated his threat. "I think they [Auckland politicians] are going to have to work on it pretty hard."

The eleventh-hour Carlaw bid by the renegade councillors was sent to Helen Clark on Thursday - the night before Mallard unveiled plans for a preferred national stadium development on Auckland's wharf.

The councillors' letter said there were "compelling" reasons for exploring Carlaw Park as the venue for the new stadium - including proximity to public transport and the central city, and the fact it is not in a residential area. However, Mallard said the derelict former league ground had been considered and rejected.

He said the land had already been committed for private development, and a stadium development would require "a number of hectares" to be sliced out of the Auckland Domain. "Starting again afresh with all these legal things overhanging it for a stadium that doesn't have any more benefits than being at Eden Park - it's just not a runner."

Hubbard has been a vocal cheerleader for the waterfront option, but councillor Penny Sefuiva said the Mayor had no right to give the project the council's unqualified support.

She said the council did not even have Rugby World Cup venue sites on its agenda until she pushed for it last month.

"I said 'Why are we sitting here like patsies, waiting for Government to do it to us? Why have we not got a view?"'

Mike Lee, chairman of the Auckland Regional Council, dismissed Carlaw Park as a viable option and said the regional authorities must concentrate on the choice given to them by the Government.

"Believe me, I've seen all sorts of weird and wonderful proposals that nothing would surprise me.