Research suggesting electric cars are often less environmentally friendly than petrol ones because of their energy consumption has merit and advances New Zealand's case to create renewable energy and better public transport, the Green Party says.
A report by Clive Matthew-Wilson, the author of car-buyers' magazine the Dog&Lemon Guide, said a high percentage of the world's electricity was produced using "dirty" fossil fuels like coal, and widespread introduction of electric cars could increase the world's reliance on coal in order to keep up with the increased demand for electricity.
The report, titled The Emperor's New Car, said claims that electric cars are "emissions free" were wrong, as they simply transferred the pollution from roads to power stations.
The report, which was prepared in consultation with recognised energy experts, focused on Tesla electric sports cars, saying they had heavy, inefficient batteries and were frequently powered by electricity from highly polluting power stations.
"Not only will electric cars not reduce emissions," the report concluded, "they may actually increase emissions, because burning coal to make electricity to power an electric car creates more pollution than if you simply powered the same vehicle using petrol".
In New Zealand's case it was the only country out of five surveyed where the Tesla was considered greener than a standard Lotus Elise.
That was because a high proportion of New Zealand's energy production is renewable.
Green Party transport spokesman Gareth Hughes said the method of energy production was a key aspect of the report.
"In New Zealand our proportion of renewable electricity has been declining over the past two decades, so if we do want to use electric vehicles as a solution (to reducing emissions) in the long term, we need to reverse that trend and produce more renewable electricity," he said.
With most of the world's energy being produced from fossil fuels, electric cars were not always as green as what people believed, he agreed.
In New Zealand, which had about 70 percent of its energy provided from renewable means, the impact was less significant.
"So I guess it's an argument that we should go for 90 or 100 percent."
In the medium- to long-term, it could still be beneficial to encourage people into electric cars here, Mr Hughes said.
"In the short-term it is about driving less and focusing on more alternatives to driving your car -- public transport, better walking and cycling."