The Green Party says the Government is ignoring the huge social cost of letting Auckland's Sky City casino extend its operations.
Five children were found locked inside a van in the casino's carpark on Sunday while their parents gambled inside.
The Government is brokering a deal with the casino to extend its licence and change a law so it can add gambling tables and machines.
In return, the casino operator would fully fund a $350 million convention centre.
The Green's Gambling Spokesperson Denise Roche says child abandonment would escalate if the Government goes ahead with its plan.
She says the Government has not factored the economic cost of more problem gambling into their economic equation when considering the convention centre.