An oil-free New Zealand is on the Green Party's agenda.

At the party's "Picnic for the Planet" on Waiheke Island yesterday, co-leader Jeanette Fitzsimons warned of an oil crisis within 10 years.

"The end of cheap oil is coming towards us with the force of a tsunami and New Zealand is not ready," she said.

Oil consumption had been so extravagant that in one century the world had used up about half of the planet's resources and demand was continuing to grow.

When the half-way point in oil reserves was reached - known as peak oil - it would become physically impossible to increase production and an oil crisis would occur, she said.

The Government last year acknowledged the peak oil point and has estimated it will be about 2037, but Ms Fitzsimons said there was a consensus among independent petroleum geologists that it might be less than 10 years away.

When the point was reached, prices would rise inexorably.

"At first it will cost you $3 per litre instead of $1 to fill up your car. Later, there will be absolute shortages, no matter what you are prepared to pay.

"The costs of farming, fishing, manufacturing and international trade will skyrocket and our international markets will no longer be able to afford our butter."

Ms Fitzsimons said the only answer was to learn to use energy more effectively.

The Greens have a number of ways they would achieve this, such as doubling the efficiency of NZ's cars, trading less low-value bulk goods globally, using less air transport and more high-tech wind-assisted shipping and producing more local food.

"I cannot disguise the enormity of the task we face," Ms Fitzsimons said. "It is no less than to transform our civilisation so it can meet the challenges of peak oil, climate change and ecological collapse."

In October, the Government launched a discussion document on sustainable energy that acknowledged the world and New Zealand faced serious problems regarding oil and said New Zealand's current energy habits were unsustainable.

Yesterday, Energy Minister Trevor Mallard, who took over the role from Pete Hodgson in December's Cabinet reshuffle, said industrialised nations had to look more closely at alternative forms of fuel.

"But that timescale depends on the discovery or lack of discovery of oil deposits around New Zealand and the world."

He said it was good for the Greens to point out that the world did have issues.

Ms Fitzsimons also addressed New Zealand's political environment, saying National Party leader Don Brash belonged to another era and, when he took the podium at Orewa this month, would not propose any solutions to the challenges of the 21st century.

The Greens hoped to work with Labour, despite policy differences, after the election, she said.

"We will use our influence to support the steps Labour is taking to protect our country from these threats and build a sustainable future."

Missing from Ms Fitzsimons' speech was any mention of genetic modification, the issue that caused tensions between Labour and the Greens after the last election.

The Greens polled 5.4 per cent in the Herald-DigiPoll December survey, well above Act, United Future and the Maori Party.

WHAT IS PEAK OIL?

Peak oil is where global oil production peaks and, due to continuing demand, prices escalate to a point where current uses are not sustainable.