The Government is being questioned by a prominent economist over whether it's got the infrastructure in place to manage the success of its Clean Car Discount.
Major changes to the scheme were announced on Tuesday morning. New Zealanders purchasing a hybrid or electric vehicle were now in line for a higher rebate.
However, low-emitting petrol vehicles were now ineligible.
New Zealand's highest emitters were supposed to be funding the revenue-neutral program. However, a faster-than-expected take-up of electric vehicles has seen demand outweigh the fees collected.
"It's directly aimed to incentivise one lot of vehicles at the expense of the others," economist Bagrie told AM on Tuesday. "The bigger picture, to me, is around the question of infrastructure, particularly whether we've got the infrastructure around New Zealand to keep up with [EV purchases].
"I think there are some pretty big question marks on this side of the equation."
More than 100,000 Kiwis had taken advantage of the rebate before the changes were announced on Tuesday.
Earlier this year, the Government announced a plan to boost New Zealand's EV charging infrastructure but could not provide details about the cost.
Meanwhile, as part of the latest changes, the Government has also slapped increases on fees paid by higher-emitting vehicles - including utes.
"The maximum charge on the most-polluting vehicles increases from about $5000 to around about $6900," Transport Minister Michael Wood said.
Wood said, overall, "cleaner vehicles still get a good discount".
"We encourage that shift," he told AM. "[The changes will] make the scheme more fiscally sustainable."