UPATED 9.42pm: The Government's taking the highly unusual step of involving itself in legal proceedings to get the $1.2 billion Three Kings quarry housing project in Auckland off the ground.

It's joining forces with Auckland Council and Fletcher Construction in the legal action.

Two groups are appealing the decision to develop the sight into a 1500 apartment and townhouse community.

They want a lower density housing project, but Environment Minister Nick Smith says that's unrealistic.

"There would be more than 1000 fewer homes, and those homes would all be priced in the high-million dollar figures. Now that is not the sort of housing development that is going to help us resolve both the supply and the affordability issues."

"If the appeal is successful, the bottom line is this quarry will sit as an ugly eyesore for Auckland for another decade or two, and there'll be 4000 fewer people without a quality home to live in."

Dr Smith said as Auckland house prices continue to rise, they're having to deal with over-crowding and all the problems that go with that.

"That is why the Government is going to be pulling every lever at its disposal to increase the supply and affordability of housing [...] and that's why we've chosen to join these proceedings on this specific development at Three Kings."

Local Board member Michael Wood says the Government and council have sided with Fletcher over the local community.

He claims information obtained under the Official Information Act shows they've been in extensive contact with Fletcher Residential about the issue.

Mr Wood says they had a different plan that would involve a thousand homes rather than 1500.

He says the local board has supported good quality compact city development on the site in its plan for the quarry site.