Key Points:

The $500 million waterfront stadium price tag could rise, Finance Minister Michael Cullen warned yesterday.

His caution over costs came as a big downtown Auckland developer joined urban design experts in opposing the project and Herald readers delivered by a four-to-one margin an emphatic thumbs-down to the waterfront plan.

In another day of fast-moving developments:

* Prime Minister Helen Clark rejected criticism of the location, saying "it regenerates that whole waterfront downtown area".

* Auckland Regional Council chairman Mike Lee said the ARC was "deadly serious" about meeting the Government's deadline of November 24 for a "yes" or "no" answer.

Dr Cullen said whether the $500 million waterfront stadium or the $385 million upgrade of Eden Park was chosen, there could be cost rises over the next three or four years from the impact the building boom in China and elsewhere had on steel and concrete prices.

Helen Clark said there were several compelling reasons for the waterfront site, particularly for multiple use for major sporting, entertainment and spectator events.

Responding to criticism from city design experts that the location could wreck the waterfront, the Prime Minister was confident Aucklanders could decide on an option that allowed Auckland to host the Rugby World Cup.

A waterfront stadium "would be an asset and I think that over time Auckland is going to look at how it regenerates that whole waterfront downtown area".

"Having it as a major entertainment, recreational precinct, with the ability to host large events, I don't think is a bad thing at all.

"As a passionate Aucklander and a passionate New Zealander, I want to see our international city of scale, which is Auckland, host this cup and I think most Aucklanders do."

Mr Lee said councillors and officers had identified a list of issues that needed to be worked through to come to a decision. The main focus would be the effect on Ports of Auckland from taking land for a waterfront stadium and the cost of mitigation.

The ARC owns the ports company through its investment arm, Auckland Regional Holdings.

Mr Lee said the ARC was taking up Sport Minister Trevor Mallard's offer to talk to a team of Government-appointed port exports, led by former Centre Port chief executive Ken Harris, and receive its technical report on the site option between Bledisloe and Captain Cook wharves.

Mr Harris has been asked to brief the councils but not talk to the media while "commercial" negotiations take place with the ports company.

Mr Lee said the ARC was "deadly serious" about meeting the November 24 deadline. A "yes" answer would give the Government certainty about ports land for a stadium. "No" would be endorsing Eden Park, he said.

The waterfront site came under further attack from the developer undertaking a $350 million heritage and urban renewal at Britomart.

Bluewater chief executive Matthew Cockram said he shared the concerns of architectural guardians and, in particular, their concerns for the Britomart project to preserve 18 heritage buildings and reconnect their shipping and merchant links with the sea.

The stadium choice has clearly polarised opinions. Former All Black coach Fred Allen doesn't want to leave his beloved Eden Park, but John Hart, who also coached Auckland and the All Blacks, said: "Given my background, my history and heart are clearly with Eden Park.

"However, accepting the well-stated problems with a multi-purpose stadium in a suburban residential area, I think we need to take a bold and visionary approach."

For that reason, he said, he favoured a new venue that would invigorate downtown Auckland and leave a legacy beyond the World Cup.

Mr Cockram said he was worried about the bulk of a 60,000-seat stadium right in front of several low-rise heritage buildings on Quay St and the effect it would have on sea views.

It made more sense to put a stadium further to the east on Bledisloe Wharf, an option discarded by the Government because of the impact on Ports of Auckland's operations.