The Government has asked SkyCity to return to the drawing board over its $250 million to $300 million national convention centre for Auckland.

The state liked what it saw, but wanted more.

Outlining how SkyCity could spend $627 million in the next three years, chief executive Nigel Morrison said the Ministry of Economic Development asked for a larger floorplate for the centre, which is the company's largest planned project in Australasia.

The vast building has been lowered from five to four levels at 101 Hobson St, a site SkyCity already owns near TVNZ and uses for administration and training for the much bigger "mother ship" on the other side of Hobson St.

An airbridge over Hobson St would link the company's Albert St and Federal St properties into the new centre for 5000 banqueting guests.

"We had some feedback from the ministry that they thought the scale of our proposal was not quite large enough and they wanted a 10,000 sq m floor plate," Morrison said. He presented new images with 20 per cent extra floorspace. To get that area, SkyCity needs a TVNZ property and Morrison said he was hopeful.

No decisions had been made on the convention bids, Morrison said, speculating that this was because the Government's focus was on earthquake-torn Christchurch.

Bids competing against SkyCity for the new centre have come from The Edge, incorporating the historic St James, Ngati Whatua, Infratil and ASB Showgrounds.

SkyCity's next most ambitious real estate plans are for a $250 million splash in Adelaide, redeveloping and expanding its casino there.

A $40 million spend-up is planned for the Darwin casino, aimed to be finished by 2012.

Two other Auckland projects are starting: the Gambling Commission-approved high-roller precinct for SkyCity above its Auckland hotel where $27 million will be spent, and a Federal St upgrade for $10 million to be ready for the Rugby World Cup.