Speedway is due to move from Western Springs in 2019 to a new location, due to be announced by Regional Facilities in the next few months.
Regional Facilities Auckland chief executive Chris Brooks said the original $12 million was for an international cricket oval and there was potential to fully develop the site with lighting, corporate box facilities and possibly some covered seating.
Brooks has also hinted at competing with Eden Park for T20 and one-day cricket matches at Western Springs, which could have a capacity for 23,000 to 25,000 spectators.
"Clearly you wouldn't take anything up(to council) for a major development that is based on one or two test matches," Brooks said.
The upgrade looks certain to exceed Regional Facilities' $30 million stadium strategy budget, including $11m for upgrading Mt Smart Stadium for the Warriors, and will require political approval at a time of financial restraint.
Councillor John Watson said the latest "lavish and nonsensical" proposal had blown out from $12 million to up to $70 million.
"It's incredibly wasteful and unnecessary at a time when we are under huge financial pressure," Watson said.
Eden Park Trust Board chairman Doug McKay said Regional Facilities' latest proposal was news to him.
"If the ratepayer are silly enough to approve another ground when it's not really necessary, well, New Zealand Cricket is in the box seat," said McKay.
He said the outer oval, or No 2 ground, at Eden Park was the ideal boutique cricket location for test matches, although it does have logistical and size constraints.
New Zealand Cricket chief executive David White has told the Herald that it views the development of a viable test venue in Auckland as a priority.
He said the NZC board has received presentations from Auckland Cricket on a proposal to develop the outer oval at Eden Park and from Regional Facilities to develop Western Springs.
"Once all information has been collected and discussed, the board will be in a position to state a preference," White said.
